1146916 - pulp-puppet-module-builder now builds modules without init.pp files

This addresses both of the following bugs: 
 * https://bugzilla.redhat.com/show_bug.cgi?id=1146916
 * https://bugzilla.redhat.com/show_bug.cgi?id=1146834

The tool will now attempt to build a module from any directory containing a `Modulefile` (the old metadata file) or a `metadata.json`. The one exception is if the module is in a `pkg`  directory(e.g. `puppetlabs-mysql/pkg/puppetlabs-mysql/metadata.json`), which is created when `puppet module build puppetlabs-mysql` is run
I was trying to think if there was a way to do this that was a little more OS agnostic. We don't currently work on Windows, but it is largely due to so many places where we assume Unix-like paths. There is os.path.split(), but that doesn't split all the way like you've done here. It wouldn't be that hard to make something that does though, I don't think. Either way, it's not a blocker so you can leave it as is if you like. Supporting Windows would be a lot of effort as it is anyway.