Add useClientRequest fetchData tests with warnings

[jackdclark]

Implements the tests that were left out of #30
Resolves #31

    fetchData
      ✓ calls request with options & updates the state with the result (10ms)
      ✓ calls request with revised options (2ms)
      ✓ skips the request & returns the cached data if it exists (2ms)
      ✓ skips the cache if skipCache is passed in (2ms)
      ✓ skips the cache if skipCache is there is no cache (2ms)
      ✓ sets the result from the request in the cache (2ms)

The following warning will display in the console for each test until facebook/react#14769 has been resolved. This is because fetchData updates the state & should be wrapped inside an act, however act does not yet support async/await & fetchData is an async function.

  console.error node_modules/react-dom/cjs/react-dom.development.js:506
    Warning: An update to TestHook inside a test was not wrapped in act(...).

    When testing, code that causes React state updates should be wrapped into act(...):

    act(() => {
      /* fire events that update state */
    });
    /* assert on the output */

    This ensures that you're testing the behavior the user would see in the browser. Learn more at https://fb.me/react-wrap-tests-with-act
        in TestHook
        in Wrapper