Since all Elm functions are pure we have a guarantee that the same input
will always result in the same output. This module gives us tools to be lazy
about building Svg that utilize this fact.
Rather than immediately applying functions to their arguments, the lazy
functions just bundle the function and arguments up for later. When diffing
the old and new virtual DOM, it checks to see if all the arguments are equal.
If so, it skips calling the function!
This is a really cheap test and often makes things a lot faster, but definitely benchmark to be sure!