Ease ability to invoke flush_batch directly

```flush_batch``` is useful enough to invoke directly, but it requires an argument which can be omitted as empty hash.
Merge pull request #182 from from brainopia/master

Ease ability to invoke flush_batch directly
Support removal of multiple columns
Merge pull request #183 from brainopia/remove_multiple_columns

Support removal of multiple columns
Update changelog and version number
Add native dynamic composite decoding.
Merge pull request #184 from nearbuy/optimized-dynamic-composite

Add native dynamic composite decoding.