Expanding the util test suite

As part of an introductory software engineering course (15-313) at Carnegie Mellon, we (@schallert, @jchoi1, @lindzy, @shuaisha, and @dingty) are submitting additional tests for the util package.
If you consider this to be a fail state, you might consider using `t.Error` instead of `fmt.Print*`. See http://golang.org/pkg/testing/.