Reset gem path after installing Overcommit

When running the Overcommit hook when Overcommit has not been installed,
the user is asked to install it. However, after installation you could
not load the `overcommit` gem since the gem path was already cached.

Fix this by resetting the gem path.

Change-Id: I868edd68ef4603610faf3d8f98f648f2691dfe38
Reviewed-on: http://gerrit.causes.com/35619
Reviewed-by: Shane da Silva <shane@causes.com>
Tested-by: Shane da Silva <shane@causes.com>

Author: sds

template-dir/hooks/overcommit-hook

@@ -27,6 +27,7 @@ rescue LoadError
 
   if (answer = gets) && answer.strip.downcase.start_with?('y')
     if system('gem install overcommit')
+      Gem.clear_paths # Reset load paths so newly installed gem is found
       require 'overcommit'
     else
       puts 'Unable to install Overcommit'