Merge pull request #13 from khandelwal/master

Refactoring of the Layers Interface
Removing unused libraries
First stab at interpretations layer
Readability fixes
Merge pull request #14 from cmc333333/master

Interpretations Layer
Terms layer pre-processing
Given the pre_processed terms, build the term layer. Also, modify Layer base class so that pre_process actually gets called.
Be a little tighter when determining which paragraphs contain definitions
Merge pull request #15 from cmc333333/terms-layer

Terms layer