Add failing spec for CONFIGURE_OPTS word-splitting
Fix mis-quoting of CONFIGURE_OPTS

This fixes cases like:

    ruby-install ruby 2.0.0 -- CFLAGS="-march=x86-64 -O2"

Which were getting incorrectly word-split into two arguments.
Use * not @ when passing options to ./configure
Merge pull request #65 from pbrisbin/master

Fix mis-quoting of CONFIGURE_OPTS