Split node.js code into own file

[natevw]

Since npm takes care of all the file mess, we might as well keep the main fermata.js primarily focused on browser, with only stubs to require the node.js–specific stuff. We're already doing this somewhat with the oauth helpers, but there's a few more chunks of other SLOC that could be moved out too.

[mik01aj]

Looks like a duplicate of #40.

[natevw]

It's related, but this would include the _nodeTransport helper and perhaps a bit of other logic. It's really not a great deal of code though and might be more trouble than it's worth for some of the functionality (I'm thinking autoConvert form helpers and such), so this is fairly low priority.