Compile just one fs/fsx file

[dredgy]

Hi, first off - love the project. I think F# is great syntax for scripting and being able to use it with ease of use of PHP is awesome. Can't wait to see where this goes.

Tiny feature request, if possible to just compile one file at a time instead of the whole project. Is just a bit quicker in workflow as I have the compiler set to run every time I save a file.

Cheers