Define a couple of constants to allow render testing and export Client as module
Handle keyboard input

* Store keyboardState inside client instance as an object
* bind key up and down events to set keyboardState
* Define #cloneKeyboardState method in order to avoid messing with state when storing pendingInputs (close future :)
* BOOM!
Process keyboard inputs and render entity

* Define Client#update function, responsible to process inputs and render state
* Client#processInputs defines deltaModifier to make entities move smoothly,
clones current keyboard state to define the next input and applies it on
main entity, so it mooooves
* Cient#render renders all entities defined in this.entities (only main entity right now)
BOOM!

* Main js file is queries the DOM, instanciate objects and set loops
* Update client 60fps
* Define basic HTML structure with a canvas to see stuff
* build/ folder has the browserified version of main.js .. should be deleted when gulpfile is properly defined..