This minor release of Quick introduces "focused" examples.

You can use focused examples as a way of running only a subset of all
the examples in a test suite. If there are any focused examples in a
test suite, only those examples are run. If there are no focused
examples, all examples are run.

- You can define focused examples using `fit`.
- You can define focused example groups using `fdescribe` or `fcontext`.
  All examples within focused example groups are treated as focused
  examples.
- You can define a focused set of shared examples using `fitBehavesLike`.

In addition, pending examples now use the same underlying architecture
as focused examples. Both are built atop of "filter flags". Filter flags
are arbitrary String-to-Bool maps that are associated with any example
or example group. You can configure Quick to include/exclude certain
examples, using QuickConfiguration and its new filter methods.