Typo correction: Excepted -> Expected'
Use fmt.Errorf when appropriate.
Gofmt -s (simplify)
Simplify the NopWriter code.
Implement several golint suggestions, including:

* Removing type declarations where they're inferred
* Changing Url -> URL, Id -> ID in names
* Fixing snake-case names
Merge pull request #1111 from cespare/style-fixes

Style fixes