This addresses issue #13: seeding convertTokenization with the proper character offset.

It also bumps the version to 2.0.1-SNAPSHOT.

Previously, convertTokenization assumed the starting character
offset was 0, thereby affecting the token textspans, which
according to the concrete thrift spec, should denote the
"location of this token in the original text."

Conveniently, convertTokenization is only called from
convertSentence, which itself takes an offset parameter.