Upgrade openssl-1.0.1k

Closes #664, closes #682

Prior to this we tried to use pre-built LLVM binaries since Yosemite,
but starting with Rubinius 2.3.0 this is no longer a feature of its
build system. Instead, look for "llvm" Homebrew package and suggest
installing it if it's missing.

Add Ruby 2.3.0 dev definition

Closes https://github.com/sstephenson/ruby-build/issues/689.

Added definition of Ruby 2.2.0

add jruby-1.7.18

Add definition of Ruby 2.2.0-rc1

Final dist filename change for JRuby 9000.

Add jruby-1.7.17

http://www.jruby.org/2014/12/09/jruby-1-7-17

Highlights:
  56 issues fixed for 1.7.17
  native crypt()
  Fixed bad encoding of string interpolated within backticks
  popen2+ now works properly with env hash
  improvements to align MRI and JRuby FFI
  updated stdlib to 1.9.3p392 (+ rexml security fixes)
  tzdata updated

JRuby 1.7.16.2 has been released to address CVE-2014-8090.  All users
are encouraged to upgrade

http://jruby.org/2014/12/08/jruby-1-7-16-2.html

Added definition of 2.2.0preview2

Fixes #667, closes #668

When requested via `-h|--help`, usage text should be displayed on stdout
and the exit status should be 0.

When usage text is shown due to invalid arguments, it should be
printed to stderr and exit status should be 1.

Use exactly the same arguments that would have `ruby-build` succeed at
executing, but add one more extra to test argument counting.

- rbenv-install accepts 0 or 1 argument
- rbenv-uninstall accepts 1 argument
- ruby-build accepts 2 arguments

JRuby 9000 is now 9.0.0.0 (official version number for release).

`assert_failure` only accepts an expected message as argument, and only
if it matches the output in full.