Verified that the parser can handle import cycles.
Import cycles are detected before running `go test -cover`, which causes an infinite loop (known bug in go cover tool). Fixes #228
Now using %#v for formatting assertion failures when using the ShouldResemble and ShouldNotResemble functions. Fixes #246 and builds on what was done in #217
Now serializing more detailed representations of stuff when assertions fail using ShouldResemble. Further addresses #246