Reccomend Catch integrations with popular IDEs on Running Tests page

If the cpp track will be sticking with Boost for unit testing, it may be worth mentioning on the [Running the Tests page](http://exercism.io/languages/cpp/tests) that there are addons for many popular cpp environments to support boost in a friendlier way.

For example:
>If you're developing with a common IDE like Visual Studio, you may wish you install plugins for Boost Testing, if available, that can make unit testing a little friendlier. Here are a few examples [for Visual Studio 2017](https://marketplace.visualstudio.com/items?itemName=VisualCPPTeam.TestAdapterforBoostTest), and [Visual Studio 2015](https://marketplace.visualstudio.com/items?itemName=ETASGmbH.BoostUnitTestAdapter).

Note that I've only tried the one for 2017. This could be kept as a VS-only note, or try to find similar addons for other popular IDEs if they need it.