Command line argument to determine lexer based on filename only

[JakeWharton]

I'd like pygments to attempt to determine a lexer based only on the filename via the command line. This is useful when the filename is known as well as the contents but the file does not actually exist on disk anywhere.

[masseria]$ ./pygmentize -N test.py
python
[masseria]$ ./pygmentize -N test.java
java
[masseria]$ ./pygmentize -N test.sh
bash
[masseria]$ ./pygmentize -N test.klajdfklj
text

I've included a patch to add this functionality.

[gbrandl]

Thanks, added in [c97ce1d7c205].