Merge branch 'hotfix-issue-16'

Correct an issue where the extension fails to load properly for
first-time users.
Merge branch 'dev'

* Workaround for inversion not applying to whole window
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
Merge branch 'dev'

Changelog for release 0.6.0:
  * "Smart" mode got more smarter
  * New options page to control advanced settings and workarounds:
    - This is the new home of the "Forget Site Customizations" button,
      so it's not so easy to accidentally click during normal use.
    - Can now force or disable the hardware rendering path used as a
      workaround for high DPI blurriness.
    - Can enable a new experimental feature to uninvert animated GIFs in
      "Smart" mode.
  * Fix for full screen not being inverted on short pages.
  * Reduced white flicker in many situations.
  * Other minor fixes and cosmetic tweaks.
Quick fix for PDFs not rendering

Add a short (50 ms) delay before inserting the CSS link tag to work
around a Chrome bug preventing PDFs from rendering. This is a band-aid I
need to fix with a better strategy.
Bump version to 0.6.1