Test against various Ruby implementations
Add Rubinius standard library gems
Use Ruby 1.8-compatible hash syntax
Replace stabby lambda with lambda keyword
Move dependencies from gemspec to Gemfile (expect for Bundler)

Bundler's Gemfile gives you the ability to differentiate between
development dependencies and test dependencies. Non-test development
dependencies (e.g. guard) do not need to be installed in the continuous
integration environment, making the build somewhat faster.

This leaves bundler as the only dependency specified in the gemspec,
since it is needed to bootstrap dependencies specified in the Gemfile.
Add newline at the end of each file
Replace ::BasicObject with Naught::BasicObject
Define to_c/to_r with conversion methods in pre-1.9 Ruby versions
Conditionally define respond_to?/respond_to_missing?

I tried doing the same thing with alias_method/undef_method but it
caused errors on JRuby.
Ruby 1.8, Rubinius, and JRuby do not print the indication of blocks
Fix specs on Rubinius
Fix specs on JRuby