Added eval method to Time, allowing to write complex time calculations naturally i.e. 1000ms + 10s - 1f
Added first unit tests using Mocha and Should.
Added arithmetic string parsing to Timespan as well, allowing i.e. Timespan.str "1s+2f .. 20s"
Time.toFrame now uses floor to make calculations more predictable.
Added unit test for Timespan.segmentByInterval.
Added math.round utility.
Added .s setter and getter to Time.