Added a stopwatch class
Added a stopwatch class

Stole a stopwatch class from taskflow,
https://github.com/openstack/taskflow/blob/master/
taskflow/utils/misc.py#L450

Will use this in the serializer code.

Change-Id: Iac2dce8ec0cb421534d9fd12956fcad7b191bfb9

stackforge/entropy,stackforge/entropy,stackforge/entropy