Add 2 more settings that should be changed in ~/.s3cfg to match Riak CS' app.config

See discussion here if needed: http://lists.basho.com/pipermail/riak-users_lists.basho.com/2013-March/011514.html

It appears the Riak CS Fast Track misses one step which is configuring the `host_base` and `host_bucket` parameters in `~/.s3cfg` config file. They default to Amazon S3 values, resulting in an error when you try to run certain operations on Riak CS (at least creating a new bucket with "s3cmd mb").

I tried to keep the wording coherent with the rest of the doc but feel free to improve it.

**NB** : I don't speak Japanese at all so I didn't update `source/languages/jp/riakcs/tutorials/quick-start-riak-cs/index.md`, which might be required before merging this pull request.

Thanks