RC crawler

I like the RC crawler from [triafgg](https://www.thingiverse.com/thing:3340951)
But my last printed one's chassis rail was broken, so I am trying to redraw it by myself.
 
Here are some changes:
1. Put battery at rear side, ESC & receiver at front side
2. Rear cover can be opened
3. Reset shocks position on body & shock bracket
4. Make chassis rail as 5mm
5. Make chassis rail lower than original, also less holes
6. Upgrade for bonnet with bumper
7. Make 2 holes on bumper for LED li