Fix #1198, enable custom locale in template rendering, fixes links

reverts getpelican/pelican@ddcccfeaa9

If one used a locale that made use of unicode characters (like fr_FR.UTF-8)
the files on disk would be in correct locale while links would be to C.

Uses a SafeDatetime class that works with unicode format strigns
by using custom strftime to prevent ascii decoding errors with Python2.

Also added unicode decoding for the calendar module to fix period
archives.

pelican/tests/test_contents.py

@@ -2,7 +2,6 @@
 from __future__ import unicode_literals, absolute_import
 
 import six
-from datetime import datetime
 from sys import platform
 import locale
 
@@ -10,7 +9,7 @@ from pelican.tests.support import unittest, get_settings
 
 from pelican.contents import Page, Article, URLWrapper
 from pelican.settings import DEFAULT_CONFIG
-from pelican.utils import truncate_html_words
+from pelican.utils import truncate_html_words, SafeDatetime
 from pelican.signals import content_object_init
 from jinja2.utils import generate_lorem_ipsum
 
@@ -127,7 +126,7 @@ class TestPage(unittest.TestCase):
 
     def test_datetime(self):
         # If DATETIME is set to a tuple, it should be used to override LOCALE
-        dt = datetime(2015, 9, 13)
+        dt = SafeDatetime(2015, 9, 13)
 
         page_kwargs = self._copy_page_kwargs()