Dev ignore submatches

[greena13]

Context

The current action matching behaviour of react-hotkeys has caused confusion and seemed to contradict user's expectations a couple of times (#161, #181, #175): It first examines <HotKeys/> components closest to the element currently in focus, and then moves towards the top of the app, examining the full hierarchy of focused <HotKeys /> components, before moving on to <GlobalHotkeys/>.

The trouble is that submatches are allowed in this matching process: If an application has a context-dependent action, bound to a short key combination (e.g. ?) and a longer global action bound to a longer key combination (e.g. shift+?) the longer key combination is hidden behind the shorter one and never triggered whenever a child of the <HotKeys/> component that defines the shorter combination is in focus.

This pull request

• Adds a new allowCombinationSubmatches configuration option to enable submatching and disables it by default (i.e. submatching is turned off by default)
• Moves around some Readme sections and adds a more in depth description of how the key matching algorithm works, together with its customisation options and the tradeoffs.
• Updates the test suite to cover the new expected behaviour for both configuration option settings.