Added Token/Tokenizer and PostaggedToken/PosTagger Serialization

The serialization scheme is
The@0 DT NP \t big@4 JJ NP
---
Token
--------
PostaggedToken
-----------
ChunkedToken
Added ChunkedToken stringFormat Serialization
Changed token serialization parser to accept @ sign in the token string
Merge pull request #28 from jgilme1/moreSerialization

Added Token/Tokenizer and PostaggedToken/PosTagger Serialization