Added ability to get short time identifiers for TimeSpan

I needed the ability to get "ms", "s", "h", etc time identifiers.

For example, `TimeSpan.FromHours(2).Humanize()` I'd like to be able to have `"2 days"`or  `"2d"`
Please change this to `TimeSpanHumanize_{0}_{1}{2}`. This is to keep `TimeSpanHumanize` keys consistent and also keep this naming consistent with Single/Plural variations.