merge with asynchbase 9a6f32fef1d98acc08a6a2bc983eefb9869c0b5d

streaming filtering callback is not implemented for protobuf versions of hbase yet
make filtering callback work with protobufs
Use ScanFilter as a base to implement column filters on get requests
add exception handling for callbacks
add timestamps and filters to get protobuf requests
correctly serialize BinaryComparator into a protobuf
optimize commit
Merge pull request #2 from Flipboard/hbase_merge

Hbase merge with latest 1.5.0 from openTSD