cleanup

this covers a few things:

- [x] some renaming in `nsqadmin` that's been annoying me
- [x] I started using [`goimports`](https://github.com/bradfitz/goimports) and I applied it to the codebase (it separates standard library from third-party imports, which I happen to like)
- [x] moved the options code to [`go-options`](https://github.com/mreiferson/go-options) (and added the ability to specify a deprecated option)
- [x] deprecated `--max-message-size` and added `--max-msg-size` (using above) - it was the only command line flag that spelled out `message`
- [x] fixed all data races in tests and now `test.sh` runs a second pass with `GOMAXPROCS=4` and `-race` (when available)
- [x] cleaned up tests that didn't use `mustStartNSQD` and changed that function to use `/tmp` for data path