Fixed some annoying bugs & made some improvements:

- scroll up functionality didn't correctly update the heat map, causing
  the front end to redraw incorrectly;
- the algorithm to determine what area to repaint in the Swing frontend
  was incorrect, causing incorrect repaints. This was masked by the fact
  that the entire display was repainted as well (which is obviously not
  what we want);
- changed the heat map from an array of booleans to a BitSet to reduce
  the memory usage a bit while retaining the same semantics;
- changed the CharBuffer to accept an array of Integers instead of an
  List. Also added a unit test to verify its functionality;
- allow the input for the terminal to come from a different source than
  an InputStream. Added a new connect() method that allows you to
  specify only an output stream, and added writeCharacters() methods to
  allow writing to the terminal directly;
- allow a different input/output character encoding to be specified.
Released v1.1.0 of jVT220.