upgrade pty.js dependency

chjj/pty.js#26 makes node-ChildDaemon unusable in node >= 0.9.x. this
change updates the dependency.

i'm also curious -- shouldn't this be in `dependencies`, not
`optionalDependencies`, since the module won't work without it (on
non-win32 systems)?
Merge pull request #1 from aaronj1335/update-ptyjs

upgrade pty.js dependency