first experiment : no more async switches, new method to block without
blocking the event loop
[ ABSOLUTELY NOT READY ]
Get max_age to respect graceful_timemout

This an experiment towards solving #537
Some code can probably be merged with Watcher.begin_stop and Watcher._final_stop
Merge pull request #2 from amarandon/async_experiment

Async experiment with max_age
still some experiments
Merge branch 'async_experiment2' into async_experiment

Conflicts:
	circus/watcher.py
making process with stop command
start to work
add some hints
unit tests ok
set command is now asynchrounous (because of restart)
add a space for flake8/travis build
some progress
some details
exclusive locks between some commands
rm_watcher is now async
more robust (for unit tests)
fix some new problems with unit tests
skipping some tests because they block the whole process
Initial version of the CommandReloader plugin
Follow test naming convention for plugins
Fix interpretation of loop_rate option