first pass at compiling under 2.11

make use of magnet pattern to get ride of overloading conflicting with default parameters
refactor build

- pull dependencies and custom shell prompt out of Build.scala
- bump to sbt 0.13.5
- replace Build.scala with build.sbt
- refactor dependencies (use provided scope for AWS SDK for published artifact)
magnetize the rest of the DynamoDB mapper API

- batchDeleteByKeys
- batch load by keys
- count query
- delete by key
- load by key
- query
migrate from deprecated ProgressEvent codes

- now using the general progress event notification
http://aws.amazon.com/releasenotes/Java/1003850039868229
bump dependency version numbers
Merge pull request #19 from pellucidanalytics/topic/migrate-2.11

Migrate to Scala 2.11
Merge branch 'unstable' as v0.6.0

Pull in latest changes from unstable branch:
- Pull request #19