Icons: Add red color to octicon-x

Failed Travis builds should have a red "X" next to the commit ID
README: improving readability; removing contribution list
clarifying and providing examples on the spacing
Use proper class selector to colorize octicon-x
Merge pull request #138 from Poorchop/octicon-x

Icons: Add red color to octicon-x
Releases: Fix top border
Merge branch 'master' of https://github.com/StylishThemes/GitHub-Dark

* 'master' of https://github.com/StylishThemes/GitHub-Dark:
  Use proper class selector to colorize octicon-x
  clarifying and providing examples on the spacing
  README: improving readability; removing contribution list
  fix contributing links
  Add CONTRIBUTING.md file. Fixes #135
  Icons: Add red color to octicon-x
Discussions: Fix linkifed code tag color
Update CONTRIBUTING.md

removing the "not enforced" bit as it could get confusing to someone after reading the K&R bit.
Discussions: Fix label text color
Issues: Fix label color by letting GitHub's magic take over, #139
Organization Members: Fix name color
version bump
fix attribute link selector