bump tachyon dependency to 0.4.1
Fixed mismatched ordering after multiple data load

The TablePartition and TablePartitionStats are not inserted in the same order within the RDD when multiple data load is performed. This may cause problem in partition pruning. For detailed description of the problem, please refer to https://groups.google.com/forum/?fromgroups#!topic/shark-users/8VQZmRNCVQk
Merge pull request #220 from harveyfeng/rewrite

AST transformations for DISTINCT aggregates
Conflicts:
	src/main/scala/shark/SharkDriver.scala
Merge pull request #267 from sundeepn/astrewritefix

AstRewrite for count distinct can cause unexpected issues with certain queries
Merge pull request #314 from twleung0507/master

Fixed mismatched ordering after multiple data load
Merge pull request #313 from haoyuan/master

bump tachyon dependency to 0.4.1
Patch 'null' prompts for non "shark" exec modes
Disable rewrites for rollup, cubes, and limits.

We also output a warning when a LIMIT is used for COUNTs
Merge pull request #300 from harveyfeng/rewrite-09

AST transformations for DISTINCT aggregates
Extract Tachyon interface to allow pluggable off-heap storage clients
Enable OFF_HEAP caching via "CACHE <table> IN off_heap"
Retitle "tachyon" to "off-heap" everywhere.
Properly handle uncaching/recaching tables
Address Reynold's and Harvey's comments
Address Round # 2 of Harvey's clients