use bash string manipulation and install Gemstone to
add MagLev to list of Rubies
add url link for MagLev
Don't pass libffi prefix to Rubinius

Since they vendor libffi, this is unnecessary. Refs #23.
Use RUBY_INSTALL_DIR instead of SHARE_DIR.

* Calculate RUBY_INSTALL_DIR wrt $BASH_SOURCE.
Merge pull request #26 from jacknagel/patch-2

Don't pass libffi prefix for Rubinius
Merge pull request #25 from havenwood/maglev

Log Gemstone install to $SRC_DIR and use bash string manipulation
Style.
Fixed the source line.
Set RUBY_SRC_DIR for maglev.
Ensure that MagLev is installed exactly where we want it.
Ensure that the gemstone symlink points to an absolute path.
Moved link to the bottom.
point MagLev link to MagLev's homepage rather than repo
Move the install.sh command into configure_ruby.
Remove empty functions.
Comment.
Prefer the style of extracting the binary arcive, then mving it into place.