fix React `propTypes` warning in tests

We are currently generating a bit of noise in the tests because of React warning on props.

Warning: Failed propType: Required prop `ariaLabel` was not specified in `PaginationLink`.
Warning: Failed propType: Required prop `range` was not specified in `Slider`.
Warning: Failed propType: Required prop `start` was not specified in `Slider`.
Warning: Failed propType: Required prop `range` was not specified in `Nouislider`.
Warning: Failed propType: Required prop `start` was not specified in `Nouislider`.
Warning: Each child in an array or iterator should have a unique "key" prop. Check the top-level render call using <div>. See https://fb.me/react-warning-keys for more information.
Warning: Failed propType: Required prop `setIndex` was not specified in `IndexSelector`.
Warning: Failed propType: Required prop `hasResults` was not specified in `undefined-AutoHide`.
Warning: Failed propType: Required prop `hideWhenNoResults` was not specified in `undefined-AutoHide`.
Warning: React.createElement: type should not be null, undefined, boolean, or number. It should be a string (for DOM elements) or a ReactClass (for composite components).
Warning: React.createElement: type should not be null, undefined, boolean, or number. It should be a string (for DOM elements) or a ReactClass (for composite components)

We’ll have to clean that. I also think our propTypes checks are not really in sync with the code

[vvo]

we can get rid of those by calling NODE_ENV=production mocha… in the test script, this should do it (if we expect them)

[bobylito]

On it!