Support stats for cached partitioned tables, take 1
Decouple SharkContext from SQLSuite. Put it in a SharkRunner singleton so that we can run SQL queries across different test suites.
Support stats for partitioned tables, take 2
Simple test suite for stats collection and pruning for partitioned tables
Patches for partition stats and pruning
Tachyon support

Includes
- LOAD, INSERT, ALTER commands already supported on
  heap tables
- Partitioned tables
Test suite for Tachyon support
Patches for partition stats and pruning
Some docs for MemoryTable, updates based on review.
Remove extraneous line in TachyonUtilImpl
Merge pull request #237 from harveyfeng/tachyon-support

Tachyon support
Merge MemoryTableReader and TableReader, plus misc updates based on review.
Merge branch 'master' into part-stats

Conflicts:
	src/main/scala/shark/execution/MemoryStoreSinkOperator.scala
	src/main/scala/shark/execution/OperatorFactory.scala
	src/main/scala/shark/execution/TableReader.scala
	src/main/scala/shark/parse/SharkSemanticAnalyzer.scala
Correctly detect Tachyon connections. Don't run TachyonSQLSuite if Tachyon isn't running...
Merge pull request #235 from harveyfeng/part-stats

Support stats for cached partitioned tables