Golint

Ran through the whole master branch with both golint (https://github.com/golang/lint) and go vet (the built-in static analysis tool) and fixed a myriad of small, non-critical things. 

There are still a bunch of public structs / methods lacking comments (which golint disapproves of) and some other stylistic issues (use of _ in variable/package names, ALL CAPS const names, etc) which I didn't touch but could use a tune-up.