Added Afterglow theme.
Merge pull request #163 from YabataDesign/master

Added Afterglow theme.
Add link to Desert Night Color Scheme
Merge pull request #164 from fgb/master

Add link to Desert Night Color Scheme
No longer rely on being inside GitGutter directly

* Use relative imports
* Determine plugin_dir to load icons from
Change how icon paths or determined for #167
Capture ValueError along with ImportError

For issue #168
It appears the new relative imports I was using was throwing an
unexpected error in ST2 and breaking.

In the future I should probably not use Error handling for flow control
like this and just determin the ST version and then use the appropriate
import method.
Only use plugin_dir in ST3

This will prevent ST2 from using GitGutter-EDGE
but at least git gutter will work in ST2 until
I figure out a way to get __file__ to work correctly
Update README.md
Added Cobalt2 as a supported colour scheme
Merge pull request #175 from wesbos/patch-1

Added Cobalt2 as a supported colour scheme
Merge branch 'master' of https://github.com/jisaacks/GitGutter