Rename Fiber::this() to Fiber::getCurrent()

Update readme and stubs

Clarify getReturn() behavior

Restore Fiber::this()

Plus cleaned up some now unnecessary code.

Add Fiber::getReturn()

Drop FiberScheduler

Refactor FiberScheduler

Add isStarted() method to Fiber and ReflectionFiber

Swap static constructor for regular constructor

Refactor suspending

Use Fiber::this() to get the currently executing fiber, then only pass the FiberScheduler to Fiber::suspend().

Provide FiberScheduler to suspend callback

Split ReflectionFiber into two classes

Update stubs

Drop Continuation object

Separate Fiber::run() into two methods

Allows for creating fibers without such deep nesting and adds ReflectionFiber::fromFiber().

Rename continued to isPending

Add Continuation object

Drop Awaitable interface

Redesign Future as Awaitable

Update stub

Make Scheduler an interface

Scheduler fiber is created by calling Scheduler::run().

Add Future interface

Use callback given to suspend to resume fiber