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
Add rbenv-install tests
Auto-discovery of build definitions from rbenv plugins

The `share/ruby-build/` directory from each rbenv plugin, if it exists,
is added to RUBY_BUILD_DEFINITIONS automatically during `rbenv install`.
add ruby-1.9.2-p330
Merge pull request #615 from hone/ruby-1.9.2-p330

add ruby-1.9.2-p330
Merge pull request #614 from sstephenson/rbenv-plugin-definitions

Auto-discovery of build definitions from rbenv plugins
Read ruby-build revision from git if available

But don't assume that RUBY_BUILD_ROOT is where ruby-build's own files
reside, since RUBY_BUILD_ROOT can be overriden with alternate definition
files location.
Faster clone of Bats in CI

Avoid cloning the whole project's history which we'll never need
Merge pull request #612 from sstephenson/git-revision

Read ruby-build revision from git if available
add jruby 1.7.14 build
Merge pull request #620 from patricknavarromahoney/master

add jruby 1.7.14 build
add jruby-1.7.15
Merge pull request #624 from chulkilee/jruby-1.7.15

add jruby-1.7.15
ruby-build 20140905
Don't log files as they're extracted from tarball

The `-v` option for tar has been here since the beginning of ruby-build,
but it's not really informative to see a list of files in the log as the
list of files is guaranteed to be the same across machines since we do
checksums.
Print configure options when openssl ext failed to compile

This helps to debug whether `--with-openssl-dir` was used properly.
Indicate ruby-build version number on build failures

This might save us from having to ask people which version they have
installed when they paste us build output from the console.