Switch HamlLint hook to use extract_messages

Simplify hook by using helper provided by Hook::PreCommit::Base.

Change-Id: Icbf45532487a02502cd0395ded5798545436ffd5
Reviewed-on: http://gerrit.causes.com/44902
Tested-by: jenkins <jenkins@brigade.com>
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>