Preserve source tree structure with -o option + CoffeeScript source maps

This allows compiling a whole source tree to JS, with source maps if
desired, into a new directory with the same structure.

The CoffeeScript compilation feature also now respects the -m parameter.
This closes #176.

Also removes some seemingly useless `loadFile` calls, speeding up
compilation.
Merge pull request #211 from goffrie/tree

Preserve source tree structure with -o option + CoffeeScript source maps