Add new ngram record-based type and accompanying functionality
Add new ngram record-based type and accompanying functionality

 - Add a (NG a) record type for easier access to an ngram's
   text, length and other inormation. The ngram field in NG a
   is a Maybe, obviating the need for the old NGram a type. Nothing
   function as part of the Monoidal identity.

 - Add Functor instance for (NG a). Allows for operations on the
   text part, but not the length. Mostly, the information should
   be immutable.

 - Added a Monoid instance to facilitate adding NGs together.

 - Added ngInject. An empty T.Text ("") results in the monoidal
   indentity for NG.

 - Added NG and ngInject to the export declaration.

 - Cleaned up excess spaces from end of file.

R-Morgan/NGramCrackers