add cmds descriptions
pre && post action declaration
change input format
change input format, add environments variables
first checks implementation
In [1]: from pumphouse import checks

In [2]: p = checks.PumpHouseShellCheck({"input": ["127.0.0.1", "127.0.0.2", "10.0.0.3", "10.0.0.4" ], "env": {"COUNT": 1}, "cmd": "ping -c\${COUNT} ^" });

In [3]: print p.run()
['10.0.0.4', '10.0.0.3']
review fixes
fix typo
simplify shell commands
don't run if null input
Add exception when check failed
Merge remote-tracking branch 'origin/taskflow-checks'

Conflicts:
	doc/samples/api-config.yaml