Coffee compile command now executes for just *.coffee items.

This resolves an error that would sometimes occur on Mac OS X:

    node_modules/.bin/coffee --compile  .

    /Users/will/edx_all/edx-platform/node_modules/coffee-script/lib/coffee-script/command.js:486
        cwd = process.cwd();
                      ^
    Error: EMFILE, too many open files
        at compileOptions (/Users/will/edx_all/edx-platform/node_modules/coffee-script/lib/coffee-script/command.js:486:23)
        at compileScript (/Users/will/edx_all/edx-platform/node_modules/coffee-script/lib/coffee-script/command.js:158:15)
        at fs.stat.notSources.(anonymous function) (/Users/will/edx_all/edx-platform/node_modules/coffee-script/lib/coffee-script/command.js:143:18)
        at fs.readFile (fs.js:176:14)
        at Object.oncomplete (fs.js:297:15)

I think this is because the node script has a bug in which it opens all the files it wants to compile, but doesn't close the file handles until it finishes executing (see node_modules/coffee-script/lib/coffee-script/command.js line 136).

@cpennington does this seem like a reasonable fix?