New mode: Dim

Just reduce the brightness of a page.
Add dim level slider for dim mode
Correctly uninvert YouTube previews
Fix inversion of dynamic iframes

This includes Twitter previews on certain sites.

Fixes issue #34
Improve popup description logic

The changes made for the dim slider slightly altered the logic used by
the popup to display what scheme is in use. Restore that part of the
logic to the old behavior.
Fix inverted images in Hangouts app

When Chrome is configured to allow extensions access to chrome:// URLs,
this extension can get injected into some Chrome apps (like Hangouts).
Update the injection logic to not always assume Deluminate has been
injected into the topmost window, and supply a fallback to checking the
tab URL (apps don't have a real tab) with the window's baseURI.
Fix icons in Google groups
Invert PDFs in Gmail and elsewhere
Document new "Dim" mode
Update version to 0.5.0
Style dim slider consistently across OSes

It looked pretty awful at least in Windows.
Fix fullscreen workaround not always applied

Handle a race condition where the workaround doesn't get inserted if the
DOM is not complete.
Fix page not inverted when extension reloaded
Sync CSS/JS injection settings

It probably doesn't actually affect anything, but sync the injection
settings for extension start with the same settings in the manifest.
Respect itemprop=photo microstyle

Don't invert these "photo" images in smart invert mode.
Fix popup width in Chrome 38

For some reason, the width calculation has changed in Chrome 38. Make it
dynamically adjust the width to the width of the widest label by not
allowing labels to wrap.
Merge branch 'dev'

Changelog for release 0.5.0:
  * New mode: Dim (with selectable amount)
  * Now able to invert PDF files
  * Fix issue with inverted embedded Youtube previews
  * Fix issue with inverted embedded Twitter images
  * Other minor fixes and improvements