[Converge] Replace 'io.js' with 'node.js'

[jasnell]

This converged repo is node.js. At some point, we'll need a global rename in docs and source back to node.js, and to ensure the compiled binary is node and not iojs.

[andrewdeandrade]

Began work on this here:

nodejs/node#50

[rvagg]

Handled by nodejs/node#2367