Fixes from golint and go vet.

[golint](https://github.com/golang/lint) and `go vet` pointed out a number of cleanups that could be made on the code base. This PR addresses those suggestions, cleans up the relevant comments, and changes the README signing section to describe the current behaviour.
I'm sure it works, I'm just scared that it might break later because *other* files are changed and the two modules are not imported anymore.

Really just a point of safety/style, you can totally ignore it if you want.