Improve mysql_grant to work with IPv6.

This work attempts to improve the situation for matching IPv6
IP addresses, as the previous regex couldn't handle them properly.
Merge pull request #308 from apenney/fix-grants

Improve mysql_grant to work with IPv6.
Previously we were matching to ensure that usernames matched
user@host but MySQL allows you to use @host with a blank user.

No longer .select but allow all and remove these successfully.
Add in the @host users.
Updated my.cnf template to support items with no values
README.md update and format tweaks

The section for mysql::client didn't specify that package_name and package_enable were available parameters.

Also took the liberty of making the override_options sections identical between ###Overrides and ###Parameters->mysql::server->override_options, as well as marking various other items as `code`, for a prettier display.
Merge pull request #317 from StephenBrown2/patch-1

README.md mysql::client parameters update and format tweaks
Merge pull request #312 from apenney/fix-no-user

Previously we were matching to ensure that usernames matched
Merge pull request #316 from tekenny/master

Updated my.cnf template to support items with no values
Prepare -rc4 release.
Merge pull request #318 from apenney/200-rc4-release

Prepare -rc4 release.