If alerts

We now have two types of alert. I've made them a component and will go around and update other alerts in apps to use the new ones. I know there were some issues with alerts in thorntree using hyperlinks and not working with a component so will look at that (still useful everywhere else).

I also removed a couple of old and pointless typography variables.

![image](https://cloud.githubusercontent.com/assets/814861/3808468/ebe8bccc-1c77-11e4-8f6c-d131a0dcc6f0.png)