Update contributing guidelines

Author: vinkla

CONTRIBUTING.md

@@ -6,9 +6,9 @@ Contributions are welcome, and are accepted via pull requests. Please review the
 
 * Please follow the [PSR-2 Coding Standard](https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-2-coding-style-guide.md) and [PHP-FIG Naming Conventions](https://github.com/php-fig/fig-standards/blob/master/bylaws/002-psr-naming-conventions.md).
 * Ensure that the current tests pass, and if you've added something new, add the tests where relevant.
-* Remember that we follow [SemVer](http://semver.org). If you are changing the behaviour, or the public api, you may need to update the docs.
-* Send a coherent commit history, making sure each individual commit in your pull request is meaningful. If you had to make multiple intermediate commits while developing, please [squash](http://git-scm.com/book/en/Git-Tools-Rewriting-History) them before submitting.
-* You may also need to [rebase](http://git-scm.com/book/en/Git-Branching-Rebasing) to avoid merge conflicts.
+* Remember that we follow [SemVer](http://semver.org). If you are changing the behavior, or the public api, you may need to update the docs.
+* Send a coherent commit history, making sure each individual commit in your pull request is meaningful. If you had to make multiple intermediate commits while developing, please [squash](https://git-scm.com/book/en/Git-Tools-Rewriting-History) them before submitting.
+* You may also need to [rebase](https://git-scm.com/book/en/Git-Branching-Rebasing) to avoid merge conflicts.
 
 ## Running Tests
 
@@ -20,12 +20,12 @@ First, install the dependencies:
 $ composer install
 ```
 
-Then run phpunit:
+Then run PHPUnit:
 
 ```bash
 $ vendor/bin/phpunit
 ```
 
 If the test suite passes on your local machine you should be good to go.
 
-When you make a pull request, the tests will automatically be run again by [Travis CI](https://travis-ci.org/) on multiple php versions and hhvm.
+When you make a pull request, the tests will automatically be run again by [Travis CI](https://travis-ci.org/) on multiple PHP versions and HHVM.