use broadcast send in rpc
seperate send and send_raw functions.
still make rpc_id of broadcast in seperate range
use _rpc_id_generator for all clients and broadcast messages
use send_raw instead of call_raw in forall function.
Merge pull request #95 from EasonLiao/rpc_broadcast

use broadcast send in rpc
A few simple performance optimizations.

The Traits library overrides __reduce__ex__; if we override it
ourselves we can make things a bit faster.

Reduce logging.  Python logging is terribly slow.
Merge pull request #97 from spartan-array/perf-tweaks

A few simple performance optimizations.
Merge branch 'master' into from_file_parallel