Revert mixed argument patch for addNode(), because addNodes() in loadJSON already supports single string argument.
Revert mixed argument patch for addNode(), because
addNodes() in loadJSON already supports single string
argument.

shigeruNakajima/springy,dhotson/springy,pingjiang/springy,dabobert/springy,kidylee/springy,dabobert/springy,drstarry/springy,tigerleapgorge/springy,shigeruNakajima/springy,tigerleapgorge/springy,kidylee/springy,pingjiang/springy,dhotson/springy