Fixes optional parameters handling (client / server).

--HG--
branch : cluster
add peer node: return channel name.

--HG--
branch : cluster
Node: add event firewall (client / server).

--HG--
branch : cluster
Node: fixes the event value issue.

--HG--
branch : cluster
Node: fixes event response flood.

--HG--
branch : cluster
Add node examples.

--HG--
branch : cluster
rename : examples/hello_node.py => examples/node/hello_node.py
rename : examples/nodeserver.py => examples/node/nodeserver.py
Merged in treemo/circuits/cluster (pull request #71)

Node: multiple fixes
Rename the FallbackErrorHandler to FallbackExceptionHandler and the event it listens to to exception
Merged in prologic/circuits (pull request #72)

Rename the FallbackErrorHandler to FallbackExceptionHandler and the event it listens to to exception