Expand `else` to `True` instead of `otherwise`.

Makes `if` syntax independent of the value/type of `otherwise`.

Fixes these bugs: http://share-elm.com/sprout/52b8d0fee4b06194fd2d36cc and http://share-elm.com/sprout/52b8d636e4b06194fd2d36cd . 
I've included the first as a test case since it's compile-time error.