It accepts a list of CoffeeScript file paths on stdin
and for each <path>.coffee file in the input, it writes
a <path>.js output file containing the converted,
reformatted source.

The result is ES2015 source so will require some
fixups as long as we're using ES5 in the main app
codebase.

The current transformation process involves:

 1. Performing an initial CoffeeScript -> JS
    conversion with 'decaffeinate'

 2. Applying some fixups for common issues, currently
    done with dumb string modifications.

    In future I might look at writing a Babel transformer.

 3. Parsing the source with Babylon to check that it is valid ES2015
    If not, the user is prompted to go and simplify the CoffeeScript
    so that decaffeinate can process it correctly.

 4. Reformatting the source with typescript-formatter, which
    takes care of indentation and high-level formatting.

 5. Running the source through JSCS' fix mode which deals
    with smaller details.