Merge MemoryTableReader and TableReader, plus misc updates based on review.
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
Merge patches
Correctly detect Tachyon connections. Don't run TachyonSQLSuite if Tachyon isn't running...
add sleep before talking to shark server