[ADAM-360] Upgrade to Spark 1.1.0.

Fixes #360.

Upgrades to Spark 1.1.0. This is API compatible with Spark 1.0.1, so no major changes were needed. The changes were restricted to our unit tests:

* Several unit tests were comparing the CharSequences that came out of Avro with Strings, and these tests started failing.
* Spark's [RangePartitioner](https://spark.apache.org/docs/1.1.0/api/scala/index.html#org.apache.spark.RangePartitioner) functionality changed slightly, such that you may not receive the full number of requested partitions, so I changed our test to acknowledge this.