slim down app.js:

* introduce routes.js for all of the routing stuff we were doing in app.js before
* move some default setup to environments.js
* move the socket io server to a property on the `app` object
* miscellaneous extractions (mainly there was just too much going on in app.js.
make persistent posts work better:

* include eager-loaded associations of Post (get associated User when a Post is loaded)

* update post 'fixture' with current data

* use current data scheme in the post.jade template (and associated clientside template)
add note on compiling client-side templates to README