Merge pull request #5 from blob626/master

Add (ice-9 format) module to imports for freeimage and ftgl
Merge branch 'master' of github.com:davexunit/guile-2d
Merge pull request #8 from blob626/master

Update simple example program
Merge branch 'master' of github.com:davexunit/guile-2d
Update simple example program

The example program provided in the readme doesn't work.
It seems that the on-key-down hook changed since the readme was written.
This takes bits from simple.scm to fix it.
Throw error if image file does not exist.
Tidy up freeimage module.
Merge branch 'master' of github.com:davexunit/guile-2d