Added `with_bytes` and `with_mut_bytes`
Added `with_bytes` and `with_mut_bytes`

Closes https://github.com/PistonDevelopers/image/issues/110

twoodford/image,bvssvni/image,TyOverby/rust-image,huonw/image,ruud-v-a/image,lady-segfault/image,nwin/rust-image,dtwood/piston-image,hetzge/image,PistonDevelopers/image,xanium4332/image,mbrubeck/image,tomaka/image,JaySon-Huang/image,theotherphil/image,PistonDevelopers/image