[Experiment] FastCGI support

This is an unfinished experiment, few months old. I just want to share the idea:
- run PHP or HHVM as FastCGI listening on port/socket
- run tester for example as `-p 127.0.0.1:9000`

There are crucial priblems (all workarounds you can find in `Environment` class):
- cannot get the script exit code, FastCGI protocol has options for it, but it is not supported by PHP (I didn't test HHVM)
- only runtime changeable INI values can be passed
- `$_SERVER['argv']` support

So, I don't know if there is chance to finish it to usable state.

You can try it, all Tester's tests pass me now under PHP-FCGI and HHVM too, but I'm sure that it is an illusion.

Now it is a nice toy :-)