Merge pull request #15 from euroelessar/master

Python binding update
Detect correct elliptics version in setup.py
Depend on 0.17.7 eblob and higher
Added blob_size_limit eblob parameter
Added index_block_bloom_length and index_block_size eblob config parameters
Merge branch 'master' of github.com:reverbrain/elliptics
Elliptics version update: 2.20.1.0
Added leveldb into default config
Fixed smack's sync-to-disk interval commit
Do not play with TCP_CORK. Added sending debug.
Fixed possible null dereference in dnet_send_request() debug
1. Try to send packet from thread, which calls dnet_send*() if queue is empty instead of queueing it and postpone work to net thread
2. Use TCP_CORK only for requests which total size is more than sizeof(struct dnet_cmd)
3. Use TCP_NODELAY if dnet_send_request() completes sending whole request, this flushes packets to client reducing latency
Elliptics version update: 2.20.1.1
Added dnet_send_request() comments
Return error from dnet_send_request() and propagate it back to dnet_send*() calllers.
Remove unused package_dir
Do not try to send data directly from dnet_io_req_queue() (calling thread context), queue request instead
Elliptics version update: 2.20.1.2
Use client's provided ID when possible in dnet_send_cmd_single()
Elliptics version update: 2.20.1.3