CDK-560: Set javaVersion to 1.7

 * Update javaVersion
 * Keep javaTargetVersion to 1.6
 * Update README

Closes #156.
CDK-552: Removed how to contribute from maven site

 * Updated link to point to the wiki version

Closes #159.
CDK-515: Added tests for Spark jobs reading from/writing to Datasets.

 * Added spark-core_2.10 under dependency management
 * Implemented tests that use FileSystemDataset and HBaseDataset
 * Added exclusions to the pom to fix hadoop-1 profile build

Closes #150.
CDK-489: Move DatasetRepository to the SPI

 * Moved DatasetRepository to org.kitesdk.data.spi.DatasetRepository
 * Moved RandomAccessDatasetRepository to org.kitesdk.data.spi.RandomAccessDatasetRepository
 * Added deprecated interfaces that inherit from the SPI versions
 * Deprecated DatasetRepositories
 * Removed uses of DatasetRepositories from the code and test code

Closes #158.
CDK-551. Use Hive's public API for metastore operations