Add Debian wheezy support for default version fact

Debian Wheezy has a default version of 9.1, but doesn't currently have
an operatingsystemrelease value beyond 'wheezy'. This command searches
for wheezy in the operatingsystemrelease fact and sets the fact value
accordingly.
Merge pull request #59 from puppetlabs-operations/wheezy_default_version

Add Debian wheezy support for default version fact