Map loading

[jaythomas]

Goals for the week:

• [x] Get map loading working so we can use Tiled to create maps
• [x] Merge all that stuff into master
• [x] Push up a demo map branch as @marcioRene commanded
• [x] Make sure circle entities created in Tiled load properly

Side note:

[x] Get luacheck config loaded so @SuperShadowPlay stops creating global variables

[jaythomas]

@marcioRene per your request a sample map with a circle entity can be found on the branch map-demo