Added get_acquia_environment method

A fair few methods are requiring that they have access to the Acquia
environments so this fixes that.
Change method check to a switch statement instead
Refactored environment listing
Moved purge API call into a helper
Extended user listing documentation
Refactored server listing into a more reusable function
Added in the domain commands
Moved JSON parsing into helper function
Removed JSON parsing from the domain-purge requests
Dropping parenthese around acquia_api_call, like a real developer.
Added a list-svn-users command

Some people are still using SVN so listing of all SVN users has been
added.
Make it a gem
Remove extra license file
Releasing 1.0 :sparkles: