Internal Refactor

* Join primitive and definitions into a single words hash to more
* accurately reflect forth's model
Abstract stack to constant

* Introduce undefined word class
   This deals with a basic tenant of forth.  That is, any non word is
   considered an integer
* Introduce Words class
   This deals with the decision to create either an undefined word or
   fetching the word from the dictionary
Push decompile/compile logic into lower level classes

* Also renamed decompile/compile to show/expand respectively to more
* accurately reflect their meaning