Create addAndDelete method function in FakePing
Implement add method but bugging
Add node done
Delete nodes in local test
fixed a bug where lack of responses from a node would break the system
cleaned up the communication code
Replace Kill by PoisonPill to kill actor in local test
Remove unused imports
minor corrections in the comments
Merge pull request #47 from BeyondTheClouds/fixed-ping

Looks good!