Implemented new basic button widget with simple sprite. A button can be hovered over...

Implemented new basic button widget with simple sprite. A button can be hovered over and clicked and an event string can be specified to be emitted when it is clicked. Handled simple quit event in main to demonstrate.
Events are queued by the button and popped in main where they are handled. Eventually this can be moved to the Game class or whatever. Could create something where other classes can subscribe to certain events or something.
Can specify position, font, text, colour, and the event to emit on click in the JSON.
Re worked fonts in Texture.py to support multiple fonts at multiple sizes.
Changes to InputHandler to support mouse events.
screenshots for writeup.