Support adding custom properties.
For example, setting 

ssplit.newlineIsSentenceBreak' to  'always.
Alter specs to run against 
Stanford CoreNLP version 3.3.1.

* Expectations in spec/english_spec.rb
and sepc/french_spec.rb needed to be altered
to pass with 3.3.1.
Add instructions to the README for how to setup
up the gem to use the latest version of the
Stanford CoreNLP (version 3.3.1).
Little bit of clean up to README on instructions
for using the latest version of the Stanford
CoreNLP.
Merge pull request #26 from mgurley/custom-properties

Custom options and latest version of Stanford CoreNLP.