batch ingestion fixes

1) Fix path when mapped output is compressed
2) Add number of reducers to the determine hashed partitions job
manually
3) Add a way to disable determine partitions and specify shardCount in
HashedPartitionsSpec
remove unused import
Add serde test for shardCount
review comments and add partitioner
review comments- use final variables
minor fix
add all the shard specs
Merge pull request #500 from metamx/batch-ingestion-fixes

Batch ingestion fixes