Corrected wrap-80
Switched `ndim` check to `atleast_3d`
Removed `elif` from ndim check.
Updated felzenszwalb rgb test to reflect min_size fix
Update docstring multi to single & multi channel
Also Added spaces between `,` and `:` in distance function
Updated indentations, array shape specification
Updated function name _rgb > _cython
Added missing spaces in ValueError message
Updated docs