go fmt nsq_to_nsq
switch tlsRequiredOption.String to use strconv.FormatInt

This changes nothing output wise, but removes unnecessary code
and makes this method more generic for the future.
Add tls-min-version option

This adds a new tls-min-version flag that enables nsqd users
to specify a min tls version acceptable. The arguments to this
flag, <v>, follow the format of Version<v> in the tls package.

This commit adds --tls-min-version=ssl30 to the test.sh flags.
Merge pull request #513 from twmb/tls_min_version_512

nsqd: add --tls-min-version config option