Unit tests

[mustafauysal]

• tests https://github.com/bu-ist/responsive-framework/tree/develop/tests

[ashleykolodziej]

For this task, we're only moving existing tests over - no need to write new tests :)

[mustafauysal]

Let's keep this task open until all cases pass for both frameworks and custom plugin. We might need to change some assertions while moving the existing functionality to the plugin.

Also, I've added the framework as a development dependency for the custom plugin - https://github.com/bu-ist/bu-responsive-customizations/blob/develop/composer.json#L44 (this will allow us to test theme depended features inside the plugin.)