Add the ability to customize by grammar scope name

Adds the ability to customize the wrap guide position and visibility by
the grammar's scope name. This allows one to easily customize the wrap
guide for all Ruby files without having to duplicate all of the logic
for recognizing a Ruby file from the Ruby grammar, for example.
Merge pull request #15 from lee-dohm/scope-name

Add the ability to customize by grammar scope name
Update guide when grammar changes
:lipstick:
Prepare 0.20.0 release
Ignore empty scopes and patterns
Prepare 0.21.0 release
Add initial appveyor.yml
Add appveyor CI badge
Remove references to removed min with events/property
Listen for path changed on model
Always show the wrap guide

The React editor now longer requires the wrap guide to be hidden when
past the longest line.
Change CSS styles directly on element
Remove unneeded resize handler
Get char width from Editor model
Only use Editor model from inside view
Use a custom element for the wrap guide
Extend div instead of li
:lipstick:
:memo: Add missing s