v1.7 Improve efficiency and sentence detection by leaps

This should do away with issue #1. New:
* Some of the lists structed in memory have been done away with by
  using generators/iterators. That should improve the memory footprint.
* generateDatabase now has a sentenceSep parameter, which allows you
  to specify what separates sentences from one another. By default,
  this splits sentences at the characters '.','!','?' and '\n'.