improve ping api
use ping() in setPing()
use indexof component for ie8 and below
Merge pull request #157 from goinstant/indexof

use indexof component for ie8 and below
Does not emit close on incorrect socket connection
Merge pull request #154 from sweetieSong/fix/issue-168

fix issue/168
engine.io: updated build
Merge pull request #150 from jphire/fix/104_improve_ping_api

Fix/104 improve ping api