Fix #5 : perform geocoding client side

Squashed commit of the following:

commit 59f9630241993ea53e252fc3a0917083a28f9730
Author: Matthieu Allegre <matthieu.allegre@gmail.com>
Date:   Sun Jun 15 01:57:53 2014 +0200

    retrieve coordinates server side + remove geocode gem

commit 8d11ac50ea5c12f6820faed004586a4ed0c06aef
Author: Matthieu Allegre <matthieu.allegre@gmail.com>
Date:   Sun Jun 15 01:17:46 2014 +0200

    perform geocoding client-side