changed - to = for versioned install

documented here http://docs.mongodb.org/manual/tutorial/install-mongodb-on-ubuntu/
apt-get install mongodb-10gen=2.2.3
Merge pull request #106 from marengaz/master

changed - to = for versioned install
Fix changes for apt
Merge pull request #112 from hunner/patch_specs

Update spec for apt changes
adding arbiter addition to replicaset
Merge branch 'master' of https://github.com/victorgp/puppetlabs-mongodb