Remove the declaration of Test::Unit::TestCase from test/helper.rb

Test::Unit::TestCase is defined in test/unit lib.
Remove test-unit-full from development requirements
Add tests for Emacs Lisp

"test ruby-backward-sexp" in test/ruby-mode-test.elk are
ported as enh-ruby-backward-sexp-test.

I didn't port "test ruby-begining-of-expr",
because it is commented-out and enh-ruby-beginning-of-expr is not
defined now.
Remove test/ruby-mode-test.elk
Introduce with-temp-enh-rb-buffer macro
Add Rakefile for running tests
Fix indentation with interpolated strings in ruby 1.9.3

Commit: 2cc5fcb6762e5f3ca36e89be96fb7b6d274f6672 doesn't work
in ruby 1.9.3, because in Ripper in ruby 1.9.3,
the right brace of an embedded expression invokes on_rbrace,
while in ruby 2.0.0 it invokes on_embexpr_end.