Snowboarder Beta 2

Up arrow = speed boost (while on ground)
Left/right arrows = spin IceBob

Things learnt:
- IceBob has been provided a speed boost when on ground
- gravity is fixed to resemble some kind of norm
- camera zoomed out to show more of scene
- IceBob has been shrunk
- added props such as trees, boulders and clouds
- graphical fx occurs when IceBob lands on head
- fireworks explode crossing finishing line
- basic chalets added
- fixed layer order to avoid sprite collision
- end of course extended. Previously it looked like IceBob was about to fall of a cliff edge