cabal init

Only exporting an empty file for now.
ignore cabal's dist folder
also build an example program.

I couldn't figure out how to get cabal to build the demo when building
from source, but not to insall the executable on a user's machine if
they only require the library as a dependency.
simplified the cabal file

"cabal init" generated a lot of comments and blank lines. I've never
seen either in a cabal file in the wild, so I assume the convention is
to manually clean up the file, as I have done now.
GLUT hello world

The demo program now exercises GLUT, but not our non-existent event
library.