kiji-bento: EXP-420. Update to scala 2.10

Replay of commit 55bcba05910a9d632593f2e833f2003ea318d59c post Dashi 1.4.3 release
commit: https://github.com/kijiproject/kiji-bento/commit/a67949249296be42913e10751d9bbc58dbea93d3