v0.2.0

A minor rather than a patch: the floor on rasuvaeff/understudy moves to
^0.5, which Composer's caret already treats as breaking on 0.x.

• Requires rasuvaeff/understudy ^0.5. The wide range this package
  carried was worth keeping while it needed nothing newer; it now does. The
  fixture below states a claim that is only true of core 0.5.0, and against an
  older engine it would either assert the opposite or have to be skipped —
  which is a claim verified nowhere near the floor. Nobody is stranded:
  0.1.4 works against every core from 0.1 to 0.5 and carries the same adapter.
• An integration fixture pins scope isolation from this side of the boundary:
  an enclosing expectation left open, a complete nested Understudy::scope(),
  and the enclosing call after it. The interceptor asks the global
  Understudy::verifyAll() from a teardown position, which is the shape the
  defect fixed in core 0.5.0 took in practice, and nothing here could see it
  until core 0.5.0 was installable. (#14)