Updated composer config.
Added ClockInterface::sleep() and sleepUntil(), and implemented in AbstractClock (#5).
Implemented Timer and StatisticalTimer (#5)
Abandoned 'StatisticalTimer', it was getting bloated for little payoff.
Merge branch 'feature/timers' into develop
SystemClock::unixTime[AsFloat]() moved to AbstractClock, now supports suspension (fixes #53)
Changed use of compare() to more suitable convenience method (fixes #54)