Cross-compile Scala 2.10 and 2.11

[cjwebb]

Cross-Compile to 2.11 and 2.10. Also, upgrade dependencies so that 2.11 works, and bump SBT version to latest.

• Update ScalaTest dependency, and fix deprecated class usage.
• Update Akka dependency, and fix deprecated class usage.

The automated tests work for me, connecting to my own AWS account. I spent a bit of time making them work with DynamoDB Local, but I think it would make sense to put that in a separate issue/PR... along with making the Travis build use the local version.

This should help solve issue #31

[alexanderdean]

Happy to publish when @piotrga gives the word

[piotrga]

fine by me

[alexanderdean]

Hey guys - we're not using this library at Snowplow currently so can't really spare the time to manage the build and publication process. Sorry about that.