I kinda stumbled upon this by accident, but Ionic has a CDN you can find here:

http://code.ionicframework.com/

As you can imagine, it contains links for JavaScript and CSS resources and lets you grab earlier versions.

To be clear, this is not recommended for normal usage, and is especially not recommended for a PhoneGap/Cordova app. But if you are creating an online demo or using something like CodePen, this can be really helpful. I used it for my "tab button calls actionsheet demo" for a StackOverflow answer from earlier in the week.