Adding 'search' subcommand

Adding the `pod plugins search` subcommand (+ corresponding bacon tests)

* I was finally able to run `bundle install` and thus then `bundle exec rake` after installing rvm and using it to bundle my ruby environment :+1: So **this time I did manage to run the bacon tests** (and check that the ones I added successfully pass too) before submitting the PR :smiley: 
* I **didn't bump the version** (still `0.1.1`) as latest published version is still `0.1.0` (and `0.1.1` was not published yet, AFAIK)