Better catch syntax

The syntax is now changed to:

  (catch [] BODY)
  (catch [Exception] BODY)
  (catch [e Exception] BODY)
  (catch [e [Exception1 Exception2]] BODY)

Signed-off-by: Julien Danjou <julien@danjou.info>
Merge branch 'jd/catch' of git://github.com/jd/hy into pr-73
fixing up the hy site to match the new catch syntax