Replace the fuzz test with a proper fuzz test.

This old fuzz test did not exercise a fraction of the possible message
types, so it gave us a false sense of confidence.  It has been replaced
with a new one that uses reflection to generate streams of varying
message types to exercise the universe of real values.
Merge pull request #6 from matttproud/testing/replace-fuzz-test

Replace the fuzz test with a proper fuzz test.
Merge branch 'master' into bug/decode

Conflicts:
	ext/all_test.go
Improve comments.