Add self-explanatory UX

[alexcasalboni]

It'd be great if the chart would "explain itself" when you interact with it.

For example, I could select "512MB" as my current power configuration. Then, when I hover another power configuration (say, "1024MB"), the chart could show a message such as "With 1024MB of memory, you function will be XX% cheaper and YY% faster".

This way, users won't have to do all the math manually. It'd make the decision process much faster.