Upgrade to Boostrap 3

**This is a work in progress!**

- [ ] use angular ui directives where possible, not bootstrap plugins (login modal: tabs, accordion for forgotten password, tabs in options)
- [ ] see if we can remove jquery and use only angular.element
- [ ] remove all inline css
- [ ] dropsEnabled modal images alignment 
[screenshot](https://f.cloud.github.com/assets/589911/2088194/14fbcd7c-8e78-11e3-9daa-b3f29d9d8bbf.png)
- [ ] add `btn-default` class to buttons without another one
- [ ] paypal buttons breaks modal template (https://github.com/HabitRPG/habitrpg/commit/c93bc469081502d27dda4afb03769da76d66037a#diff-8e0eacf2159b11312d9ff93dac196a62R24) (https://github.com/paypal/JavaScriptButtons#javascript-api)
- [ ] review all css files
- [ ] challenges use angular ui modal when updated to bootstrap 3.1.0
- [x] Users with mounts aren't getting the hasPet class, or its' not getting applied, or something: [screenshot](http://gyazo.com/7af898d84310a1da0c3085d428ac7d56)