Added validate_arg_types method to Base to use in all classes
Added support for null to be passed when no validation required
Updated BaseTest to include a null validation value (no validation required)

Also corrected test method DocBlock
Added Mockery as a composer required-dev library
Decided to make method names camel case, so added @TODO to files to update them
Added support for validate_arg_types() method to validate classes

Class names are passed as string values & must be the full class name, including namespace.
Added basic PHPDocumentor config file
Typo correction in exception message
Added functionality to add a metabox to a plugin or theme

Plugin/Theme object creates plugin using it’s add_plugin() method.

This object can then be used to…
… add content using the addContent() method
… place the metabox using the following methods…
* addToPage()
* addToPost()
* addToCustomPostType( PostType $postType )
* addToLink()
* addToAttachment()
* addToDashboard()

Also added, for type hinting.  Will need expanding on…
* PostTypeBase class
* PostType class