Fixes failing resource queries for types including a double colon ('::')

Currently pypuppetdb fails to query for types containing a double colon:

    db.resource('Sysctl::Value')

The reason is that 'capitalize' will actually lowercase everything but the first character. `Sysctl::Value` becomes `sysctl::value` which puppetdb won't accept.

This patch ensures that types will always have the correct cases. So these calls are now possible:

    db.resource('sysctl::value')
    db.resource('Sysctl::Value')

The existing queries still work of course.