Treat the newtab page as its own site
New mode: low contrast without inverting
Render correctly on high dpi displays

Fixes #4
Refactor low contrast code

Minor restructuring of code related to enabling low contrast. Make it
more consistent with everything else.
Enable site-specific low-contrast settings
Add BSD license
Document the low contrast only mode
Minor aesthetic tweak in popup
Add option to force text input fields to be dark

Addresses issue #8
Enable the hidpi workaround without restart
Correct an embarrassing missing semicolon
Add direct link to submit a new issue
Hardcode hidpi workaround into popup

Should be harmless even when it isn't needed.
Update version to 0.4.0
Branch for release 0.4.0
Merge branch 'release-0.4.0'

Changelog
  * New mode: low contrast without inversion
  * Make new tab page distinct from google.com
  * Experimental workaround for Chrome bug with high DPI rendering
  * Can now set low contrast on a per-domain basis
  * New option to force some text fields to light on dark
  * Quick link to submit issues
  * For developers: license project with BSD-2