Tested with Rails 4 and ruby 2.0.0p353

Update tilt version (roll it back) so that tests
pass locally. (Works around uninitialized constant Tilt::CompileSite)

Readme updates: remove dead link, note that it works
with Rails 4 as well, and that it runs as a sinatra
app.
Merge pull request #42 from andyatkinson/minor_updates

Tested with Rails 4 and ruby 2.0.0p353