Ensure meditations expressions alternate properly

Hat tip to @seriouspony for the report
Require a true result, not just a truthy one

This keeps things like (def x 2) from accidentally passing.
Bump to version 0.2.1
Clean up whitespace
Remove name-spaces from koans on slurp.

There a couple of proposals at the functional-koans/clojure-koans that
will add a name-space to the koans files in order to fix an issue
related to the REPL.

If one of these pull request is merged in, then a change like this one
will be needed in order to maintain a pass on `lein koan test`.