`pdk new class` doesn't place files based on module root

From stephen:

If "pdk new class" is run from within the manifests/ directory, it should realize it is inside a module (which it does, because it doesn't give the "inside valid module" error) and do the right thing (which it doesn't).  Currently, if you run "pdk new class" from inside <module>/manifests, it will create new manifests/ and spec/classes/ directories inside the existing manifests/ directory (manifests/manifests/<class>.pp and manifests/spec/classes/<class>_spec.rb).  The expected result would be for it to create the class.pp in the existing manifests/ directory and the <class>_spec.rb file in ../spec/classes/