Merge pull request #119 from vinkla/contributing

Add contributing guidelines

CONTRIBUTING.md

@@ -0,0 +1,30 @@
+# CONTRIBUTING
+
+Contributions are welcome, and are accepted via pull requests. Please review these guidelines before submitting any pull requests.
+
+## Adding to this list
+
+Please ensure your pull request adheres to the following guidelines:
+
+- Search previous suggestions before making a new one, as yours may be a duplicate.
+- Make sure the list is useful before submitting. That implies it has enough content and every item has a good succinct description.
+- Make an individual pull request for each suggestion.
+- Titles should be [capitalized](http://grammar.yourdictionary.com/capitalization/rules-for-capitalization-in-titles.html).
+- Use the following format: `[List Name](link)`
+- New categories or improvements to the existing categorization are welcome.
+- Check your spelling and grammar.
+- Make sure your text editor is set to remove trailing whitespace.
+- The pull request and commit should have a useful title.
+
+## Rules for packages
+
+- Uses [PSR-4](http://www.php-fig.org/psr/psr-4/) autoloader.
+- Adheres to [PSR-2](http://www.php-fig.org/psr/psr-2/) as the coding style guide.
+- Listed on [Packagist](https://packagist.org/).
+- Has unit tests. At least 80% coverage.
+- [DocBlock](http://www.phpdoc.org/docs/latest/references/phpdoc/index.html) all the things.
+- Use Semantic Versioning to manage version numbers.
+- Keeps a [Changelog](http://keepachangelog.com/).
+- Utilize [Travis-CI](https://travis-ci.org/) to automatically check coding standards and run tests.
+- Have an extensive [README](https://github.com/thephpleague/skeleton/blob/master/README.md).
+- [Excludes non-essential files in .gitattributes](https://www.reddit.com/r/PHP/comments/2jzp6k/i_dont_need_your_tests_in_my_production).