Release a minor version fixing the warning in Ruby 2.0 and 2.1

[deivid-rodriguez]

Columnize seems in a very stable state: no open issues or commits for a while. Cheers to that! :)

I see that a couple of commits got out of the latest release. If there's no further development plans, maybe you could release another minor version with those commits. They fix a quite annoying waring...

[rocky]

0.9.0 is on Gemcutter now. Not sure why travis is errors in bundle install from rubygems.org, but I did try installing using gem install.

[deivid-rodriguez]

Thanks a lot @rocky, that was fast! 👍