RSpec language support in Atom

Adds syntax highlighting and snippets to RSpec file in Atom.

Forked from https://github.com/paveldruzyak/language-rspec

Influenced by: https://github.com/SublimeText/RSpec https://github.com/kazshu/rspec-snippets

Contributions are greatly appreciated. Please fork this repository and open a pull request to add snippets, make grammar tweaks, etc.