Merge pull request #32 from bvssvni/master

Upgraded to latest Rust-Empty
Implement contrast and brighten
Merge pull request #33 from ccgn/master

Implement contrast and brighten
Delete out.txt
Rearrange the library structure and implement some affine transformations
Merge pull request #36 from ccgn/master

Rearrange the library structure and implement some affine transformation...
Remove unnecessary typecasts, implement Collection for PixelBuf and add a convenience method for opening files
Upgraded to latest Rust-Empty