Release 0.21.0

+  Added support for ``ElasticNet``, ``Lasso``, and ``LinearRegression``
   learners.
+  Reorganized examples, and created new example based on the Kaggle
   [Titanic](http://www.kaggle.com/c/titanic-gettingStarted) data set.
+  Added ability to easily create multiple files at once when using
   ``write_feature_file``. (#80)
+  Added support for the ``.ndj`` file extension for new-line delimited JSON
   files. It's the same format as ``.jsonlines``, just with a different name. 
+  Added support for comments and skipping blank lines in ``.jsonlines``
   files.
+  Made some efficiency tweaks when creating logging messages.
+  Made labels in ``.results`` files a little clearer for objective function
   scores.
+  Fixed some misleading error messages.
+  Fixed issue with backward-compatibility unit test in Python 2.7.
+  Fixed issue where predict mode required data to already be labelled.