Enhancement/hyphen rage

Went a little further than I expected, but the basic crux is that I wanted percentages to be prefixed with a `-` instead of a `−` for the sake of being able to write remotely sane tests/code.

In doing so, I ported `View#formatPercentage` to use standard formatters, and made sure that the standard formatters could pass `formatPercentage`'s unit tests.