Throw on non-function listener
Fix for #223
Test added
Using top level tap module for tests
Comment removed
Merge #414 r=@kevinmehall: Throw on non-function listener

Fix for #223
Test added
Allows test/suite/net.js test to be rerun in succession.
Simplifies "tap" script.
Converts many tests to use the tap tester.
Fixes test 419 to use tap.count.