Merge branch 'release/0.2.0' into develop
Added start time iterator classes and tests.
Added TypeCheck and ran php-cs-fixer. (refs #3)
Removed dev comment.
Made current() method on Day, Hour, Minute, Second Iterator classes more
strict.
Merge pull request #49 from koden-km/feature/iterators-start-time

Feature/iterators start time (refs #3)
Added interval iterator classes. (refs #3)
Merge pull request #51 from koden-km/feature/iterators-interval

Added interval iterator classes. (refs #3)
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)
Work in progress.
Moved all ISO-8601 parsing into abstract Iso8601 class.
Moved isoString() method formatting to Iso8601 class.
Added interval formatting functions to Iso8601 class.
Interval's fromIsoString() still work in progress.