aura math expressions

There is a bug in the way that the components and expressions interact. The input field being used by the component is returning a string, and it's not properly coercing the value into the number (or other) type.

There are a couple of ways to workaround this, but keep in mind that neither of these examples are doing error checking, type validation, etc.:

1. Multiple each value by 1:

   <ui:outputNumber value="{!(v.value1 * 1) + (v.value2 * 1)}"/>

2. Use a change handler for the attribute value and coerce it as needed. This is obviously heavier-weight and more difficult to use.