add # and #> macro aliases for lambda and thunk, respectively

I'm not sure if this is too much line noise, but it makes lambda stuff
way easier:

($ (#> (alert 'here))

-->

$(function() {
  alert("here");
})
use # alias for lambda

Feedback appreciated.  I think (#(arg) …) looks pretty neat, and it's
simpler than a reader macro for anonymous lambdas.  It might be neat to
have an easy way to refer to arguments[n] inside of thunks.

Instead of (#(x) (get sibilant.tokens x)), we'd have something like (#>
(get sibilant.tokens #1))