Clean Slate

I've decided on a very different approach to Fathom.
This removes most of the code from the gem.
I will call versions 0.6 -> 0.99 the pre-production versions.
Since Fathom 0.5 couldn't do much, I don't feel bad about losing all
  backwards compatibility in a minor version change.
Update Gems and testing.

These were problems with the workflow, moving to Minitest
  more-effectively.
This also simplifies dependency management.  Uses the Gemfile
  to define the development dependencies instead of the gemspec.
Add BuildDiscreteFactor.

This takes CSV and turns it into a conditional probability table.
The factor format is purposefully lean.
Add BuildGraph.

Only handles discrete factors at this point.
The upcoming action objects will exercise factors and graphs
  so that I may end up with a data record for graphs and factors.
A graph is only the factors and the priors.  No iteration is implemented
  at this point.  Active Trails will be one way to iterate, and other
  iterators will come together as needed.
Seriously going for a minimalistic approach.