added a spawn_count stat in watcher, sended in statsd and visible with circusctl stats.
Updated tests.
(This spawn_count counter is not visible in stats publisher because publisher publish only process stats and not stats specific to watcher)
Corrected small case in Arbiter.reload_from_config which made some test fail in case of changing env during the test.
added min_cpu and min_mem parameters in ResourceWatcher plugin: restart process if under cpu value or under mem value if configured.
Added and updated tests
revert removed 'env' in arbiter.reload_from_config because 'env' problem is more extensive. see issue #465
Merge remote-tracking branch 'upstream/master'
added doc for new parameters in ResourceWatcher plugin
correction of tab/space in plugin doc
modifications according to current pull-request discutions
removed flake
added Thomas to the creds