Generate Coffeescript source maps

It would be great if we could get this working for debugging the resulting JS in Firefox. [Some](http://ryanflorence.com/2012/coffeescript-source-maps/) [links](http://tarantsov.com/WorkflowThu/source-maps-with-coffeescript-and-uglify-js/).

Currently we're reading the compiler output on stdout:

``` python
compiler = subprocess.Popen(command, shell=True, stderr=subprocess.STDOUT,stdout=subprocess.PIPE)
out = compiler.stdout.read().decode("utf8")
```

So we would need to switch to using temporary files in order to get the map file out, and then making sure it gets served up - or at least stored locally. And we would also need to think about how to stop that leaking with published sites.

Any thoughts?

Start by tracing the Python compiler subprocess that reads compiler output from stdout. Determine how temporary files could expose the CoffeeScript source map and how the map should be served or stored. Done means Firefox can use the generated map for debugging without leaking it through published sites.

Written by the indexing model from the issue text.