Merge pull request #11 from twitter/develop

Merge from twitter/storehaus
MySQL batch puts
override default multiput
add BatchedStore for writes
fix semaphore bug
sequence the inster, update, delete queries
Merge pull request #175 from rubanm/batch_writable_store

 add BatchedStore for writes
future fixes
cleaner putResult
Merge pull request #173 from rubanm/mysql_batch

MySQL batched multiPut
Merge pull request #12 from twitter/develop

Merge from twitter/storehaus
define WriteableStore interface, divorced from ReadableStores. A Store is now just the composition of a ReadableStore and WritableStore which allows the types to tell the full story. This should not break existing interfaces
writable stores should should themselves be Closable
update readme with new WritableStore ref
extra put semantics should not depend on reading semantics
add MergeableMemcacheStore
add comments, make class concrete
add unit test
contravariant value types for WriteableStores, don't force the Option type for values
change put to add, make retries configurable