100% working high-DPI/Retina images inside pages.

We now output:

  <img src="<thumb>" srcset="<thumb 2x big> 2x, <thumb 1.5x big> 1.5"/>

and mimic the srcset attribute behavior, which hasn't even been implemented by any browsers yet, using a JS polyfill.

I hacked sorl-thumbnail to produce the correct alternative-resolution thumbnails.  There's a related pull request @ sorl-thumbnail, so hopefully it will be accepted.  I also fixed up this "srcset-polyfill" JS that mimics srcset behavior - wasn't quite working for me as-is on my iPhone.
+ sorl-thumbnail custom in setup.py
Bigger img + retina on info page.
rotate the month labels so they don't overlap
restore full pages by default for page endpoint
fixes #447 - drop trailing slash from fetch docs
fixes #337 - add and document api ordering
Merge pull request #466 from groovecoder/api-pages-endpoint-full-by-default

restore full pages by default for page endpoint
Merge pull request #469 from groovecoder/api-ordering

fixes #337 - add and document api ordering
Merge pull request #467 from groovecoder/api-trailing-slash-447

fixes #447 - drop trailing slash from fetch docs
fixes #319 - make page api send proper redirects
fixes #470 - smarter page api context logic
allow filtering changes by type via API
Merge pull request #473 from themightychris/master

Enable filtering changes by type via API
history_date, history_type filtering for resources.
Merge pull request #471 from groovecoder/page-api-redirects-319

fixes #319 - make page api send proper redirects
Merge pull request #472 from groovecoder/page-api-full-context-470

fixes #470 - smarter page api context logic
Merge pull request #465 from ivanov/ppastats-fixup

rotate the month labels so they don't overlap
Allow width, height in styles on iframes.

Many iframes contain width and height as a style. We're already allowing width, height as an attribute, so this makes sense.
Get embed placeholder height/width from style attr.