MergeableMySqlStore and MySqlLongStore
fix merge unit test
make mergeable store concrete
implement multiMerge
refactor common insert and update queries
change to map
add pivoted store
Merge pull request #13 from twitter/develop

Merge from twitter/storehaus
Merge branch 'develop' into feature/pivoted_store
Merge pull request #181 from rubanm/feature/mysql_long_store

MergeableMySqlStore and MySqlLongStore
fix pivoted readable store, remove iterable store
add test for multiget
make tests closeable
make injection implicit
Merge pull request #186 from rubanm/feature/pivoted_store

PivotedStore