meg + gf = megf enhancement

[jthack]

I added a switch which will allow meg to only save the file if the gf expressions finds a hit. This is really useful if you're looking for a specific thing across a very large data set. Or if you're looking for something in the index or js files of many sites. It removes almost all false positives.

flag:
-g

example:
put this xml.json in ~/.gf:

{
    "flags": "-Hnri",
    "pattern": "xml version"
}

and then run:
meg -s 200 -g xml /web.config

It won't save off all those fake 200s.