OS X: Fixes check for OpenSSL version

We only care about Apple's OpenSSL when checking the version.  Any
other OpenSSL that happens to be in the PATH doesn't matter.
OpenSSL library updated to 1.0.1h

Previous versions of the library contain a vulnerability CVE-2014-0224.
Merge pull request #581 from deg84/openssl_101h_update

OpenSSL library updated to 1.0.1h
Fix `fetch_git` with `--keep`

Update existing git repo if exists, or clone if not exists.
The destination repo might exist if the `--keep` was supplied for `ruby-build`.
Add tests for `fetch_git`
Surely update local git working copy
Merge pull request #549 from yyuu/fix-fetch-git-with-keep

Fix `fetch_git` with `--keep`
Add rbx-2.2.9, 2.2.8 was skipped due to broken wrappers.
Merge pull request #583 from keltia/rbx-2.2.9

Add rbx-2.2.9, 2.2.8 was skipped due to broken wrappers.
add jruby-1.7.13
Merge pull request #591 from neojin/jruby-1.7.13

add jruby-1.7.13
Add rbx-2.2.10
Merge pull request #595 from mkroman/master

Add rbx-2.2.10
ruby-build 20140702
Add link to suggested build environment to README
Merge pull request #603 from wjordan/patch-1

Add link to suggested build environment to README
Add test for ruby-build definitions
Support changing RUBY_BUILD_ROOT

This is to allow specifying an alternate path where `share/ruby-build/*`
definitions reside. Useful in tests as well.
Extra definitions paths via RUBY_BUILD_DEFINITIONS

This is a colon-separated list of directories that will get searched for
build definition in order from left to right.
Merge pull request #613 from sstephenson/definition-paths

Support extra definitions paths via RUBY_BUILD_DEFINITIONS

Closes #609