Small updates trying to make Forge work here

Change SBT version, fix some compile errors I got, and add instructions to README (the instructions in the announcement email are out-of-date) - please retest them as without Delite I couldn't check everything.

These changes are not perfectly tested, but I still believe I should send them to you rather than having them sitting here.

I had a few problems when trying to install Forge, some due to version skew (I'm using an unfinished port to Scala 2.10 of wip-merge, Delite doesn't run yet), but others things can be fixed in Forge.

Against which LMS/Delite branches is Forge developed? Given that it uses an old Scala snapshot, that can't be the delite-develop/develop branch pair.