Fixed Simpletest instructions since drush does not work.
Minor improvements for README.md
Fixed line break in README.
Added Rule config entity class and schema stub.
Added a test case for saving an action as config entity and loading it.
Added a test case for a nested rule config and implemented getConfiguration() methods for expression plugins.
Fixed missing expression manager in PHPUnit tests.
Implemented config entity export of context definitions.
Renamed the config entity to rules_component.
Enable PHP 5.6 testing on Travis CI.