Match group func tests to specification

When a group does not exist, the group resource should raise an exception on action modify,
but not on action_manage.

Also update the `not_to raise_error(SpecificError)` deprecated syntax.
Cleanup commented out code
Merge pull request #2154 from opscode/btm/group_functional_tests

Match group func tests to specification
Remove space before paren (ruby warning)
homebrew_owner now tries to run homebrew as the user who owns the `brew` executable, or an optional homebrew_package resource attribute
Providing documentation for end-users, updating code with PR comment
Missed file on last commit
Fixing documentation errors
Moving documentation to a more logical place.  Also no longer dis-allowing users from running brew as root.
Fixing test