Refactored build functionality.

Refactored the build functionality out of the cli module allowing the
functionality to be embedded in other applications.
Begun adding package functionality.

Added the package command to the application class, refactored the project
loading functionality out of the build method into its own utility method.
Fix for loading a project.

Added a fix for loading a project if the output_directory supplied is None
it threw an exception.
Implemented package.

Implemented the building a packaging of the documentation into a zip file.