Restart agent if it uses too much memory:

Augment the Watchdog to restart the agent process
not only if it has been running longer than the restart
interval, but also if the agent process exceeds a
memory threshold.

The obvious way to do this would be setrlimit with a max
RSS size, and allow the process to die with a MemoryError
when it is exceeded, but the Tornado library being used
swallows MemoryErrors and allows the process to continue.

In order to ensure the process is terminated, the current
memory usage is checked in the Watchdog-reset method, and
the process is aborted if the threshold is exceeded.
initial memcache to checks.d
Added explicit declaration of supervisor file in deb script
Added a process info checker with groups management
Import pprint only for tests
Added psutil to requirements
Merge branch 'master' into mcache_checksd
memcache to checksd with tests working
Refactoring of process checker
removed debug code
Improved docs
removed old mcache check file
Removed unused constructor
Removed sys.path.append
More explicit gauge name
Added info on exact_match in the doc, fixed an error in the doc
removed memcache from collector.py
removed import sys
removing old memcache code
uses exceptions and added test for bad hosts