Abort when auto-correct causes an infinite loop.

This avoids future situations such as the one described in #1484. At the very least when you run into an infinite loop RuboCop won't hang and tell you where the loop occurs so you can go correct it, exclude a cop or report it as a bug.

Also maybe we should call `InfiniteCorrectionLoop` something else, like `LifetimeSentenceLoop` ;)
The readme changes seem totally unrelated to me.