relax pattern in shellshock_detect

catch attempts of the form illustrated at http://seclists.org/oss-sec/2014/q3/679 ie... 
env X='() { (a)=>\' /bin/bash -c "/tmp/foo /usr/bin/id"
cat /tmp/foo
Merge pull request #252 from TylerOderkirk/patch-1

relax pattern in shellshock_detect