started SDL port
fix rendering, add SDL event loop

- intro works now :)
worked on linux build, still segfaults
worked on linux build, still segfaults
moved all ease* funtions to Sprite class
- reduced duplicate code
- fixed "sequence point" compiler warnings
fixed more compiler warnings (signed/unsigned comparisons)
fix segfault caused by SDL renderer *doh*
fixed intro
handle input (1p only for now)
fix cubicEaseInOut function
- Merge branch 'master' into sdl-rewrite
- fix Arduino build
build script for linux/osx
updated README (build instructions)
Merge branch 'sdl-rewrite'