Implement code/test for `last`
Add code/test to protect against negative index.

Add test for short selectors.
Add dom constants and configuration
Implement code for `add` and `matches` WIP
Move `Selector.prototype.less` to `Selector.tail`.
Move stuff to CONSTANTS
More statics (local).

Slice instead of storing `arguments`
Rearange code and add more comments
Ensure candidates are returned in the order they were added.
Added some more tests, we should really add more.
Make sure to use UNIVERSAL