Improve tests.

[dmitshur]

• Update old import path from "code.google.com/p/go.net/websocket" to "golang.org/x/net/websocket".
• The third party package does not make the code any shorter or easier to understand. Most people are more familiar with net/http. It makes sense to use it in this case.
• Remove code that serves sourcemaps from GOROOT and GOPATH. I could not verify it had any effect. Also, GOPATH variable may not be a valid path if it contains more than one GOPATH workspace, so it's incorrect code anyway. It can be re-added if needed.

[mjohnson9]

:+1:

I'm not actually sure why I used Martini in the first place.