Updated version of RTT Exercises available

I've updated the rtt-exercises package to version 1.8.1. No big changes,
except that the Eclipse integration has improved. If you download
the tar.gz file and point your Eclipse 'File'->'Import...'->'Existing projects into
Workspace' to the tar archive, all exercises will be extracted and appear
in your Eclipse workspace. Really convenient.

On the code front, some exercises were a bit simplified (data flow, events)
and others were fixed.


This requires RTT+OCL 1.8.x. Use of Eclipse is optional, but if used,
you must use Eclipse 3.4 (Ganymede).