Adds client installation support for RHEL systems

Before this change, the module did not install the mongo client
for Red Hat systems. Ths change adds classes to manage mongo
clients. Closes issue #81.

Additionally, puppet-lint errors and some warnings were fixed.
Merge pull request #83 from hogepodge/client

Adds client installation support for RHEL systems
Spelling: mondodb => mongodb
Merge pull request #84 from puphpet/master

Spelling: mondodb => mongodb