Fix TimespanFormatter for ru, hr, and sr.

Fixes #54. 

It also removes patterns for certain rules in some locales, e.g., `"one"` for `tr` locale, but it wasn't used anyway since pluralization rules in twitter-cldr-js do not have this category. That's because pluralization rules in JS version are not as up-to-date as the ones in the Ruby version (see #46). 

So, the results returned by JS `TimespanFormatter` might still differ from the results returned by the latest Ruby version, but at least JS `TimespanFormatter` now uses the same set of rules as JS `PluralRules` class and works for all locales.