Rb192

So this is the reworked [pull-request](https://github.com/stephenharris/Event-Organiser/pull/194).

It contains three issues:
https://github.com/stephenharris/Event-Organiser/pull/194
https://github.com/coubeatczech/Event-Organiser/issues/1
https://github.com/coubeatczech/Event-Organiser/issues/2

* I also did some refactoring along the way as I noticed, that the default arguments to the `eo_get_venues_map` are specified two times.
* I used tabs instead of spaces everywhere
* I also ran the `grunt uglify` task for minification of the `frontend.js` file, all the other `.js` files got changed for some reason, too.


Is defining/ using `$non_booleans` necessary. We could just do
```
$all_atts = array_merge( $atts, $booleans_cast );
```

And remove lines 164 & 165.