use --continue when downloading tarball
keep source tarball if '--keep' or 'tar xf' fails
`rbenv install 1.9.3` lists matching definitions
Merge pull request #326 from quark-zju/keep-downloaded-tarball

Keep downloaded tarball sometimes
add jruby-1.7.4-dev
Updated README.md to use https to clone ruby-build
Merge pull request #336 from rkh/jruby-dev

add jruby-1.7.4-dev
Better target the shorten-64-to-32 workaround (#325, #319)

The previous version of this logic was causing us to
pass the flag when
 * clang is on the PATH, and
 * $CC, or 'clang' if CC unset, accepts the flag.
But this is totally wrong if we have clang installed,
haven't set $CC, and are going to end up using gcc.
We end up passing the flag to gcc, which rejects it.

The real fix is to put this in the autoconf goo in MRI
upstream -- the only correct way to decide whether to pass
this flag is after we know exactly what compiler we're using
and can test if that compiler accepts the flag.  But we can
do better than before by approximating autoconf's choice of
compiler as $CC if set, 'cc' otherwise (which will typically
be a symlink to gcc or clang or another.)

Fixes: https://github.com/sstephenson/ruby-build/issues/319
  and #325, which is a dupe.
Merge pull request #339 from gnprice/fix-shorten-workaround

Fix build failure when clang installed and not used
mruby-dev
Mention homebrew/dupes/apple-gcc42 if Homebrew is installed
Merge pull request #341 from statianzo/mruby

Added mruby
add topaz-dev
Merge pull request #342 from rkh/topaz-dev

add topaz-dev
ruby-build 20130408
cache git clone directory

if RUBY_BUILD_CACHE_PATH is set, create and maintain a local bare git
repository in this location.  The name of the git repository is based
on the git URL, so it will be shared between branches.
Address some feedback from Jeremy

* Decrease likelihood of cache collisions
* Avoid file:// urls (and therefore the need to escape)
Extract `sanitize` helper
Default RBENV_VERSION to the globally-specified Ruby

Fixes `rbenv install` in a directory with a .ruby-version file that specifies ree
Pass $RUBY_CONFIGURE_OPTS to REE installer with -c