previously we assumed the user had efm_perl.pl installed as part of the
standard vim runtime, but this isnt so for CentOS and possibly for other
distros - see issue #159. Therefore, we now ship it with syntastic
itself.
Note: efm_perl.pl just munges the output of perl into a different
format. It may be worth investigating further and writing our own
errorformat to remove the dependency on efm_perl.
