use Homebrew openssl if available

Fixes #343, references #367
Merge pull request #376 from mislav/brew-openssl

use Homebrew openssl if available
ruby-build 20130628

Closes #375.
Change protocol of the ruby-lang.org server from HTTP to FTP
Merge pull request #388 from markprzepiora/master

Change server protocol of the ruby-lang.org server in the MRI definitions from HTTP to FTP
ruby-build 20130806
Homebrew homepage location changed
Merge pull request #391 from yyuu/homebrew-homepage-location-changed

Homebrew homepage location changed
Don't set the Rubinius gems directory to the prefix

This causes tricky issues with Bundler. Bundler assumes that the
configure gem path *only* contains gems. When using this configuration
option, this is not the case.

What happens is that Bundler then removes the path for the Ruby stdlib
from the load path, because it is located inside what is configured as
the gems directory. This then breaks for example Rails applications when
using ruby-build to build Rubinius.

Also see: https://github.com/rubinius/rubinius/issues/2544
Merge pull request #398 from rubinius/fix_rubinius_gems_dir

Don't set the Rubinius gems directory to the prefix
use www.dnsbalance.ring.gr.jp
Merge pull request #399 from hsbt/use-ring-mirror

[WIP] use www.dnsbalance.ring.gr.jp