Merge pull request #357 from bpinto/contributing_guidelines

contributing guidelines

CONTRIBUTING.md

+# Contributing
+
+We love pull requests. Here's a quick guide.
+
+Fork and make your change. Make sure the tests pass:
+
+    ./script/run-tests.fish -v
+
+Push to your fork and [submit a pull request][pr].
+
+[pr]: https://github.com/bpinto/oh-my-fish/compare/
+
+At this point you're waiting on us. We usually comment on pull requests
+within a few hours. We may suggest some changes or improvements or alternatives.
+
+Some things that will increase the chance that your pull request is accepted:
+
+* Write tests.
+* Follow our [style guide][style].
+* Write a [good commit message][commit].
+
+## Style Guide
+
+* Indentation should follow the "2-space convention".
+* Keep line length to a maximum of 100 characters.
+
+### Plugins
+
+If your plugin is complex, make sure to include tests, we suggest using [fish-spec](fish-spec).
+
+### Themes
+
+Make sure to include a screenshot in your pull request. A nifty way is too post a comment with the image and link directly to it.
+
+[fish-spec]: https://github.com/bpinto/oh-my-fish/tree/master/plugins/fish-spec
+[commit]: http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html
+[style]: #style-guide