Issue 148: add kint debugger to the toolbox in dev mode
* adds kint library to autoloading as a require-dev dependency
* activate it in init.php when in DEBUG mode
documentation: http://raveren.github.io/kint/
Merge pull request #149 from mozfr/Issue-148-use-kint-debugger

Issue 148: add kint debugger to the toolbox in dev mode