xml => lxml for bs4, in pelican-import.wp2fields()
Fixes issue in devserver introduced in v3.3

Fixes an intermittent devserver problem with directory urls
containing index.html (i.e. clean urls).  It tries to send the
index.html file twice, resulting in a scrambled web page complete
with HTTP headers in the output, and sometimes Broken Pipe errors.
Add period to period_archives context. Refs #1044.

* Adds period tuple of (year, month, day) matching the time
  period of the current archive. Note that this is done
  to the archive context if period_archives.html doesn't exist.
* Adds tests to verify this.
* Adds documentation in themes.rst about period in period_archives.html.
add signal article_generator_pretaxonomy

invoked before categories and tags lists are created
useful when e.g. modifying the list of articles to be generated
so that removed articles are not leaked in categories or tags
Clarify docs re: settings file
Merge pull request #1249 from smartass101/split_articles_generate_context

Add article_generator_pretaxonomy signal
Merge pull request #1246 from fenekku/period-to-archive-context

Add period to period_archives context. Refs #1044.
PY and PELICAN env variable overrides for Make

This allows the user to set PY and/or PELICAN environment variable
overrides, which will be respected by the Makefile and devserver.sh.
If, for example, the default Python on your system were Python 3 and
you wanted to run Make with Python 2, using bash you could run
`PY=python2 make`. Refs #915.
Merge pull request #1178 from robulouski/devserver_fix

Fix issue in devserver introduced in v3.3
Merge pull request #1114 from brannerchinese/master

xml => lxml for bs4, in pelican-import.wp2fields()
Revert test-failing change from #1114
Updated github mark for notmyidea

The smallest mark GitHub provides in the bundle is 32x32. Since they
explicitly say don't resize the mark, I asked them to provide a 16x16
so we could use it. I received the 16x16 in this commit from GitHub
support.

However, they suggested we use the 32x32 and use CSS rules to adjust
the size:

"...we use the 32px for both and employ css background and background-
size rules to handle retina displays. I recommend that technique,
since retina users will see a mess of pixels for icons that small."

This sounds like reasonable advice. Should we consider migrating the
notmyidea social icons to 32x32, with appropriate CSS to adjust the
sizes?
Updated tests
32px Github logo and CSS shinker
Use absolute size for github mark
Revert to newly-revived Typogrify project

Since the Typogrify project will be actively maintained going forward,
there is no need for the fork.
Fix issue #1258

Correctly handle DEFAULT_DATE = None .
Merge pull request #1262 from utdemir/master

Fix issue #1258
multiple authors implemented
Merge pull request #1247 from paylogic/multiple-authors

Multiple authors implementation for #956