Added max_mem_abs and min_mem_abs to ResourceWatcher
Added human2bytes to utils.py
Added test for max and min abs mem of ResourceWatcher
Added documentation for max and min abs mem of ResourceWatcher
Merge remote-tracking branch 'upstream/master' into ressource-watcher-mem-abs

Conflicts:
	circus/plugins/resource_watcher.py
	circus/tests/test_plugin_resource_watcher.py
	docs/source/for-ops/using-plugins.rst
Fixed flake8 warnings, adpated tests to async architecture
Removed useless backslashes
Merged max_mem_abs and max_mem (same for min)
Rewrote util.human2bytes + unit tests
fixed doc
Fixed if syntax
Polishing code
fixed typo
Add ipython shell command
Add debug_gc option
Flake8 fix
Merge pull request #734 from scottkmaxwell/ipython-shell-command

Add ipython shell command
Merge pull request #735 from scottkmaxwell/add-debug_gc-config-option

Add debug_gc option
allow case-sensitive env vars
Crate.io doesn't exists anymore.
Update installation.rst

Update compatibility notes regarding ZeroMQ versions and add detail about how this is determined by pyzmq dependency.