Add parameter for purging vdir

The new parameter $purge_vdir in apache class gives the possibility to disable the purging of the virtual hosts directory.
Merge pull request #139 from mjanser/patch-1

Add parameter for purging vdir
Capitalize RedHat to be in-line with actual factor output
Fix vhost defined type unit test context to reflect actual test being performed.

context lists 'Debian' but test is for RedHat.
Merge pull request #171 from wolfspyre/master

Small fix to unit tests
release 0.6.0
Merge pull request #174 from bodepd/0_6_0

release 0.6.0
Merge remote-tracking branch 'puppetlabs/master' into movealong