Fixed metadata.json module name parsing

The module name inside the metadata.json is expected in the following
format: username-module instead username/module!

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Source: https://docs.puppetlabs.com/puppet/latest/reference/modules_publishing.html#another-note-on-module-names

Another note on module names
Although the Puppet Forge expects to receive modules named username-
module, its web interface presents them as username/module. There isn’t
a good reason for this, and we are working on reconciling the two; in
the meantime, be sure to always use the username-module style in your
metadata files and when issuing commands.
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Merge pull request #22 from grafjo/patch-1

Fixed metadata.json module name parsing