BUG: Fixed github stats retrieval

Currently urllib is used to retrieve a json file from Github, however
Github url used is not static url, urllib2 required to retrieve
information from Github.
Bug: alpha parameter was ignored when fill color is #000000
add option to delete empty PdfPages when closed

 - PdfPages objects can be told at initialization to delete the pdf file
   when closed, if no page was actually plotted
 - keep the default to not delete empty pdf files so current behavior is
   not changed
 - also some basic tests for it
clearer comments in test
refactor docstrings of PdfPages
pep8 clean up (file seems to have been created with indentation of 3
spaces!)
a bit more pep8 work
Updated the position of a few of the text examples because they were overlapping and hard to read.
Updated examples to be easier to read when drawn to a small picture.
Merge pull request #2476 from mattklein999/text3dDemoPositionUpdate

Updated the position of a few of the text examples because they were overlapping and hard to read.
Use dstack instead of zip to combine offset arrays in scatter.
Store transformations on collections as an Nx3x3 array, rather than a list of Transform objects.

When the collection has the same styling and only varies by offsets, use draw_markers instead.
Refactor WebAgg so it's easier to embed in other applications and run
over a server other than tornado.
Make figure larger.  Print address to console.
Let the Javascript side control when to fetch new frames.  draw_idle
sends a "draw" message to the browser.  If the browser is not already
waiting on another frame, it sends a "draw" message back to the server
which then returns an actual frame.  The nice thing about this approach
is that it's completely timerless.
Merge pull request #2156 from mdboom/scatter-speed

[Sprint] scatter plots are (reportedly) too slow
Merge pull request #2458 from tacaswell/mpl_inset_locater_pep8

pep8 clean up
Merge pull request #2453 from megies/pdfpages_keep_empty

PdfPages: add option to delete empty file when closed
Merge pull request #2420 from mdboom/webagg-factor

Refactor WebAgg so it can communicate over another web server
Merge pull request #2415 from kshramt/kshramt/fix_fill_opacity

Bug: alpha parameter was ignored when fill color is #000000