Support and test Clojure 1.4, 1.5, and 1.6 (alpha).  Fixes #8.
Use Clojure cast behavior when writing castable base types.
Release version 0.4.9.
Begin work on next iteration.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	src/clojure/abracad/avro/compare.clj
	src/clojure/abracad/avro/write.clj