Added a little error checking to "lein appengine-prepare", since putting the appengine-magic dependency into :dependencies instead of :dev-dependencies can cause confusing errors.
Added a little error checking to "lein appengine-prepare", since putting the appengine-magic dependency into :dependencies instead of :dev-dependencies can cause confusing errors.

craygo/appengine-magic-2,gcv/appengine-magic,ctdavies/app-engine