Scope PlatyPS to Specific Paths #124

Is your feature request related to a problem? Please describe.

.\docs is the default location for most folks to place anything documentation related. PlatyPS currently assumes that everything under the docs folder is a PlatyPS doc and hard fails if it's missing metdata related to MAML generation.

Describe the solution you'd like
Add the ability to scope specific files and paths to parse.

Describe alternatives you've considered

I've moved my docs to other folders, but this is an ugly band aid.