Issue #9: Allow drupal codebase to be kept up to date.
Update test.
Removing notify to restart the webserver

I think it's not needed at this step, maybe?
Merge pull request #10 from pfc2014/patch-1

Don't restart the webserver just because Drupal was installed.
Added accept_hostkey to git checkout
Only checkout the repo if drupal_core_path is not present
Only install drupal if not yet installed
Updated permissions on sites/default for drush