FreeCodeCamp

Fixes missing backslash in waypoints' instructions'

In three waypoints: [Find Numbers with Regular Expressions](http://www.freecodecamp.com/challenges/waypoint-find-numbers-with-regular-expressions), [Find White Space with Regular Expressions](http://www.freecodecamp.com/challenges/waypoint-find-white-space-with-regular-expressions), [Invert Regular Expression Matches with JavaScript](http://www.freecodecamp.com/challenges/waypoint-invert-regular-expression-matches-with-javascript) there are confusing instructions: /d+/gi instead of /\d+/gi, /s+/gi instead of /\s+/gi, /S+/gi instead of /\S+/gi.This commit fixed them.