Added list of plugins to be pulled from GitHub.

To do this I created a "Gitplugin" resource that is used to do the Git pull of each plugin and then activate it using wp-cli.

Closes #115, #66
Moving gitplugin puppet resource definition to its own file.

Makes wp.pp cleaner.
Clean up gitplugin code.

Removed a reference to external variable within the gitpluin resource.
Fixing some code styling problems to resolve travis-ci problems.
Merge pull request #135 from Mobius5150/github_plugins

Github plugins