Allow a release to be zipped

If you enable the parameter 'releases: compressreleases: true', every
release except the current wil be added to a tar.gz. This is to preserve
diskspace on the remote host.
Bugfix

Extract tar Gz Did not have a $command = in front of it, wich was
breaking the commits
Merge pull request #97 from JoeSimsen/master

Allow a release to be zipped