Keep color handling out of WP_CLI::line()

![spanish inquisition](https://f.cloud.github.com/assets/225715/646401/9f9da10c-d3cb-11e2-8eb6-272bb60971f2.jpg)

Basically, `WP_CLI::line( $message )` should become `WP_CLI::line( WP_CLI::colorize( $message ) )`.

If we don't fix it now, before 1.0, it'll never get fixed.


Tasks:

* [x] update success(), warning(), and error()
* [x] update `plugin status <slug>` and `theme status <slug>`
* [x] update `plugin status` and `theme status`
* [x] update `core version`