remove lock in executor

All callbacks are queued in one thread
add [] as splitter
Revert "remove lock in executor"

This reverts commit 7b0c6bb56eb4f5e95f27e0dff886766f4ba1b9b6.
refactor
improve multioutput
Merge branch 'master' of http://code.dapps.douban.com/dpark
fix bug
fix bug
Merge pull request #1 from tianzhongbo/dpark:master

improve multioutput, reduce used fds
shutdown executor after idle in 30 minutes
close underlying fileobj instead file to get a single stream when compressing
Merge pull request #2 from tianzhongbo/dpark:master

close underlying fileobj instead file to get a single stream when compressing
Merge branch 'master' of http://code.dapps.douban.com/dpark
fix bug in RDD.top()
reply with KILLED even it's not in executor

The task maybe failed to arrive to executor. It will be STAGING
status in slave, if not KILLED
refactor in executor.py
typo
add dialect='excel' and compress=False for saveAsCSVFile()
increase backlog to 64
direct stdout and stderr at the beginning