Merge pull request #4 from ccgn/master

Rearrange src files
Merge pull request #6 from ccgn/master

Initial implementation of the ImageDecoder trait
Merge pull request #7 from ccgn/master

Implement ImageDecoder for all Decoders
Merge pull request #8 from ccgn/master

add documentation
Upgraded Rust-Empty

Closes https://github.com/PistonDevelopers/rust-image/issues/9
Closes https://github.com/PistonDevelopers/rust-image/issues/10
Merge pull request #11 from bvssvni/master

Upgraded Rust-Empty
Merge remote-tracking branch 'upstream/master'

Conflicts:
	.gitignore