Update for SBT 0.12.2

For your consideration, a fix for SBT 0.12.2 failing to download dependencies. 

Tested by creating a `build.properties` file...

    $ cat project/build.properties 
    sbt.version=0.12.2

...and then running SBT.  I've left the `build.properties` file out of this commit: not sure if they are good practice or not.

I'll update the cookbook instructions accordingly.

Via: https://github.com/d6y/lift-cookbook/issues/51