Add `languages::english::EnglishAbbreviated`

[9999years]

This adds a new EnglishAbbreviated Language which takes advantage of the additional Language methods introduced in https://github.com/vi/timeago/pull/36 in order to produce more compact output.

I'm not sure this feature is appropriate for this library (none of the other Languages encode stylistic opinions like this), but I wanted to demonstrate the usage of the features.