Add Modulefile of modules for git repository under subdirectories  

### Make git repositories with puppet modules under a subdirectory contribute to the dependency resolution


Some times the git repository contains a group of modules as subdirectories. One example is https://github.com/example42/puppet-modules

When it happens, the Modulefile for the project specified is not being picked up, and their dependencies are not resolving. This is a feature supported by Librarian.

This pull request is addressing this issue.

To make it easier to check the error, I created a [repo](https://bitbucket.org/bltavares/example-puppet-modulefile-subdir) with a module as a subdirectory.

Then use this `Puppetfile`:

```ruby
forge "http://forge.puppetlabs.com"

mod 'apt-avahi',
    :git => 'https://bitbucket.org/bltavares/example-puppet-modulefile-subdir.git',
    :path => 'apt-avahi'
```
Before applying the patch, you will find this dir structure under `modules`:
```bash
% ls modules
apt-avahi
```

After applying the patch, the `modules` dir will contain the resolved modules:
```bash
% ls modules
apt       apt-avahi avahi     stdlib
```