fix(Climber) treat empty menus well

Previously Climber would throw an exception if passed a menu with no
items, specifically when it encoutered the `foreach` loop in
`getLeafByTarget()` that depended on Tree's `grow()` method. This
modifies the `grow()` method to return an empty array if there are no
menu items.

resolves #7

Add `Simple` Spotter

This adds the ability to pass basic simple arrays to Spotter through
Simple.

Added `compileClass()` and `baseClass` to help with CSS modification.

Added `element` to hooks, so you can modify the elements themselves.

Updated Changelog for 0.2.0.

Added Changelog.