Plugin Release: Default Hostgroup 3.0

Hi all,

Thanks to hard work from contributors, I'm happy to announce Default
Hostgroup 3.0 is now ready for use with Foreman 1.7 and Foreman
nightly (it may also work with 1.6 or earlier, but this is untested).

The major new feature is the ability to select a hostgroup based on
the incoming facts of the new host, which allows you to put hosts into
a group based on things like 'osfamiliy', 'ipaddress' or even custom
facts of your own. Multiple facts can be used for a single hostgroup
(first match wins, so it's an "OR" relationship). The values to match
against the facts are still regular expressions.

Unfortunately, to support this, we've had to make incompatible changes
to the config file format (it's now a hash of hashes, rather than
using an array) so please review the example file carefully on
upgrade. For this reason, we've also bumped the release to 3.0 (in
accordance with semantic versioning). It is possible to conserve the
behaviour of the previous format by matching your regexes to the
"hostname" fact.

Many thanks to Nate Walck for his hard work and persistance in bringng
this feature to Default Hostgroup.