added retina resolution icons
added sources files
Update description for "sublimelinter_mark_style" setting

The old description did not match the default value.
Updating JSHint to v2.1.2
Updating PEP8 to v1.4.5
Updating PyFlakes to v0.7.2
Merge branch 'retina-gutter-markers' of https://github.com/escusado/SublimeLinter into escusado-retina-gutter-markers

* 'retina-gutter-markers' of https://github.com/escusado/SublimeLinter:
  added sources files
  added retina resolution icons
Cleaning up; no need for 16px images.
Normalizing layers and renaming.