Update dotfiles

* Some options have been removed from JSHint v2.5.0
  * ref. https://github.com/jshint/jshint/releases/tag/2.5.0
* Fix before_install script to pass the test against Node v0.8
Use map-stream directly, instead of event-stream

es.map() is just an alias to map-stream.

https://github.com/dominictarr/event-stream/blob/480c38d08f5dffa34c41ac7
37456a3ea98f58d04/index.js#L12
Update readme

* Update URL of gulp homepage
* Use SVG badge instead of PNG badge