Added string match for 960020 to adhere strictly to RFC. Closes #158.

Tested with following header combinations:

Rule Fires:
curl -XGET -H "Pragma: no-cache" http://127.0.0.1/
curl -XGET -H "Pragma: no-cache" -H "Cache-Contro: no-cache" http://127.0.0.1/

Rule Misses:
curl -XGET -H "Pragma: no-cache" -H "Cache-Control: no-cache" http://127.0.0.1/
curl -XGET -H "Pragma: no-cache" -H "Cache-Control: no-cach" http://127.0.0.1/
curl -XGET -H "Pragma: no-cach" -H "Cache-Contro: no-cach" http://127.0.0.1/