v0.5.0

• you can now pass an options object to expand(),collapse(), and remove(). currently the only param is animation(boolean). Set animation to false if you want no animations to happen on a given panel
• md-expansion-panel-icon directive added. The will give you an animated arrow in both the md-expansion-panel-collapsed and md-expansion-panel-header directives.
• Minor animation updates
• README updated with better examples