[make-an-executable] Use jeweler to build gem
[make-an-executable] Setup Rakefile with Jeweler specifics

Went to a tmp directory, ran a 'jeweler reveal-ck --rspec' and stole
the good parts of the Rakefile.
[make-an-executable] Initialize version mechanism used by jeweler
[make-an-executable] Initial Gemspec
[make-an-executable] Using GLI to handle command line
[make-an-executable] Add executable: reveal-ck

This came from executing the command:

gli init reveal-ck generate

And then looking through the output.

I grabbed up:

* The version system that comes with gli, but tweaked it to read the
  Jeweler VERSION.

* The ./bin/reveal-ck and made it work in my environment.
[make-an-executable] Scrape out GLI generated flags, switches, docs
[make-an-executable] Call ```rake :presentation``` from within reveal-ck