Exposed package version parameter to splunk class

Exposed the splunk::version parameter for use in upgrading splunk
Added additional docs to init.pp
Updated Rakefile to match requirements for "Approved"

Updated the Rakefile to follow the specs laid out here
https://forge.puppetlabs.com/approved/criteria
Changed index and forward to a bool
Cleaned up strings that should have been bools

Added some verbose warning if strings get passed in when they should be
bools.