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 #314 from twleung0507/master

Fixed mismatched ordering after multiple data load