Update links to HTTPS and current 301 redirects in docs/templates/themes (#2661)

This also updates the Tumblr API to use HTTPS as documented in the
current Tumblr API docs.

docs/install.rst

@@ -5,7 +5,7 @@ Pelican currently runs best on Python 2.7.x and 3.5+; earlier versions of
 Python are not supported.
 
 You can install Pelican via several different methods. The simplest is via
-`pip <http://www.pip-installer.org/>`_::
+`pip <https://pip.pypa.io/en/stable/>`_::
 
     pip install pelican
 
@@ -43,7 +43,7 @@ options. For more detail, refer to the :doc:`Publish<publish>` section.
 Optional packages
 -----------------
 
-If you plan on using `Markdown <http://pypi.python.org/pypi/Markdown>`_ as a
+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]
@@ -53,7 +53,7 @@ Or you might need to install it a posteriori::
     pip install Markdown
 
 Typographical enhancements can be enabled in your settings file, but first the
-requisite `Typogrify <http://pypi.python.org/pypi/typogrify>`_ library must be
+requisite `Typogrify <https://pypi.org/project/typogrify/>`_ library must be
 installed::
 
     pip install typogrify
@@ -64,22 +64,22 @@ Dependencies
 When Pelican is installed, the following dependent Python packages should be
 automatically installed without any action on your part:
 
-* `feedgenerator <http://pypi.python.org/pypi/feedgenerator>`_, to generate the
+* `feedgenerator <https://pypi.org/project/feedgenerator/>`_, to generate the
   Atom feeds
-* `jinja2 <http://pypi.python.org/pypi/Jinja2>`_, for templating support
-* `pygments <http://pypi.python.org/pypi/Pygments>`_, for syntax highlighting
-* `docutils <http://pypi.python.org/pypi/docutils>`_, for supporting
+* `jinja2 <https://pypi.org/project/Jinja2/>`_, for templating support
+* `pygments <https://pypi.org/project/Pygments/>`_, for syntax highlighting
+* `docutils <https://pypi.org/project/docutils/>`_, for supporting
   reStructuredText as an input format
-* `pytz <http://pypi.python.org/pypi/pytz>`_, for timezone definitions
-* `blinker <http://pypi.python.org/pypi/blinker>`_, an object-to-object and
+* `pytz <https://pypi.org/project/pytz/>`_, for timezone definitions
+* `blinker <https://pypi.org/project/blinker/>`_, an object-to-object and
   broadcast signaling system
-* `unidecode <http://pypi.python.org/pypi/Unidecode>`_, for ASCII
+* `unidecode <https://pypi.org/project/Unidecode/>`_, for ASCII
   transliterations of Unicode text
-* `six <http://pypi.python.org/pypi/six>`_,  for Python 2 and 3 compatibility
+* `six <https://pypi.org/project/six/>`_,  for Python 2 and 3 compatibility
   utilities
-* `MarkupSafe <http://pypi.python.org/pypi/MarkupSafe>`_, for a markup safe
+* `MarkupSafe <https://pypi.org/project/MarkupSafe/>`_, for a markup safe
   string implementation
-* `python-dateutil <https://pypi.python.org/pypi/python-dateutil>`_, to read
+* `python-dateutil <https://pypi.org/project/python-dateutil/>`_, to read
   the date metadata
 
 Upgrading
@@ -126,4 +126,4 @@ content)::
 The next step is to begin to adding content to the *content* folder that has
 been created for you.
 
-.. _virtualenv: http://www.virtualenv.org/
+.. _virtualenv: https://virtualenv.pypa.io/en/latest/