Prefix Pip commands with python -m in docs

This ensures Pip commands will be executed for the current Python
interpreter and not, say, whichever Python interpreter happens to be
associated with `/usr/local/bin/pip`.

CONTRIBUTING.rst

@@ -43,7 +43,7 @@ publicly-accessible location:
 
 * Describe what version of Pelican you are running (output of ``pelican --version``
   or the HEAD commit hash if you cloned the repo) and how exactly you installed
-  it (the full command you used, e.g. ``pip install pelican``).
+  it (the full command you used, e.g. ``python -m pip install pelican``).
 * If you are looking for a way to get some end result, prepare a detailed
   description of what the end result should look like (preferably in the form of
   an image or a mock-up page) and explain in detail what you have done so far to

docs/contribute.rst

@@ -44,9 +44,9 @@ to manually create and activate a virtual environment::
 
 Install the needed dependencies and set up the project::
 
-    pip install invoke
+    python -m pip install invoke
     invoke setup
-    pip install -e ~/projects/pelican
+    python -m pip install -e ~/projects/pelican
 
 Your local environment should now be ready to go!
 

docs/faq.rst

@@ -74,7 +74,7 @@ Markdown format, you will need to explicitly install the Markdown library. You
 can do so by typing the following command, prepending ``sudo`` if permissions
 require it::
 
-    pip install markdown
+    python -m pip install markdown
 
 Can I use arbitrary metadata in my templates?
 =============================================

docs/install.rst

@@ -7,11 +7,11 @@ Python are not supported.
 You can install Pelican via several different methods. The simplest is via
 `pip <https://pip.pypa.io/en/stable/>`_::
 
-    pip install pelican
+    python -m pip install pelican
 
 Or, if you plan on using Markdown::
 
-    pip install "pelican[markdown]"
+    python -m pip install "pelican[markdown]"
 
 (Keep in mind that operating systems will often require you to prefix the above
 command with ``sudo`` in order to install Pelican system-wide.)
@@ -26,7 +26,7 @@ session and create a new virtual environment for Pelican::
     source bin/activate
 
 Once the virtual environment has been created and activated, Pelican can be
-installed via ``pip install pelican`` as noted above. Alternatively, if you
+installed via ``python -m pip install pelican`` as noted above. Alternatively, if you
 have the project source, you can install Pelican using the distutils method::
 
     cd path-to-Pelican-source
@@ -35,7 +35,7 @@ have the project source, you can install Pelican using the distutils method::
 If you have Git installed and prefer to install the latest bleeding-edge
 version of Pelican rather than a stable release, use the following command::
 
-    pip install -e "git+https://github.com/getpelican/pelican.git#egg=pelican"
+    python -m pip install -e "git+https://github.com/getpelican/pelican.git#egg=pelican"
 
 Once Pelican is installed, you can run ``pelican --help`` to see basic usage
 options. For more detail, refer to the :doc:`Publish<publish>` section.
@@ -46,17 +46,17 @@ Optional packages
 If you plan on using `Markdown <https://pypi.org/project/Markdown/>`_ as a
 markup format, you can install Pelican with Markdown support::
 
-    pip install "pelican[markdown]"
+    python -m pip install "pelican[markdown]"
 
 Or you might need to install it a posteriori::
 
-    pip install Markdown
+    python -m pip install Markdown
 
 Typographical enhancements can be enabled in your settings file, but first the
 requisite `Typogrify <https://pypi.org/project/typogrify/>`_ library must be
 installed::
 
-    pip install typogrify
+    python -m pip install typogrify
 
 Dependencies
 ------------
@@ -88,7 +88,7 @@ Upgrading
 If you installed a stable Pelican release via ``pip`` and wish to upgrade to
 the latest stable release, you can do so by adding ``--upgrade``::
 
-    pip install --upgrade pelican
+    python -m pip install --upgrade pelican
 
 If you installed Pelican via distutils or the bleeding-edge method, simply
 perform the same step to install the most recent version.

docs/publish.rst

@@ -118,7 +118,7 @@ in a wide range of environments. The downside is that it must be installed
 separately. Use the following command to install Invoke, prefixing with
 ``sudo`` if your environment requires it::
 
-    pip install invoke
+    python -m pip install invoke
 
 Take a moment to open the ``tasks.py`` file that was generated in your project
 root. You will see a number of commands, any one of which can be renamed,
@@ -139,7 +139,7 @@ http://localhost:8000/::
     invoke serve
 
 To serve the generated site with automatic browser reloading every time a
-change is detected, first ``pip install livereload``, then use the
+change is detected, first ``python -m pip install livereload``, then use the
 following command::
 
     invoke livereload

docs/quickstart.rst

@@ -11,7 +11,7 @@ Install Pelican (and optionally Markdown if you intend to use it) on Python
 2.7.x or Python 3.5+ by running the following command in your preferred
 terminal, prefixing with ``sudo`` if permissions warrant::
 
-    pip install "pelican[markdown]"
+    python -m pip install "pelican[markdown]"
 
 Create a project
 ----------------

docs/settings.rst

@@ -277,7 +277,7 @@ Basic settings
    If set to True, several typographical improvements will be incorporated into
    the generated HTML via the `Typogrify
    <https://pypi.python.org/pypi/typogrify>`_ library, which can be installed
-   via: ``pip install typogrify``
+   via: ``python -m pip install typogrify``
 
 .. data:: TYPOGRIFY_IGNORE_TAGS = []