Don't attempt to merge equal sets, or when sets are not concurrent
Revert to t2b/b2t for binary encoding pending further opt work
Use erlang t2b/b2t for binary encoding.

Use {compression, 1} by default, Settable by app env
{riak_dt, binary_compression, true|0-9|false}.
Document the compression app env var
Fix typo in docs for env var
Merge pull request #77 from basho/rdb/feature/compression

Our to/from binary was slow slow slow, use t2b (with compression)