Merge branch 'master' into joamag/color

res/videos/003-boot.gif

res/videos/004-tetris.gif

src/apu.rs

src/cpu.rs

src/devices/mod.rs

src/devices/printer.rs

src/devices/stdout.rs

src/gb.rs

src/inst.rs

src/lib.rs

src/macros.rs

src/mmu.rs

src/pad.rs

src/ppu.rs

src/rom.rs

src/serial.rs

src/timer.rs