Flesh out permutation to full length if not all dimensions are specified
No-op for ScaleNone on whole images
I/O: direct ccalls to libmagick, rather than the Cmd interface

This is approximately 10x more efficient
Add libmagick library name for Windows
Fix (and test) writing of images & arrays of different bitstypes
Fix libwand path on OSX, add BinDeps installer for ImageMagick
Implement writemime using libwand

Fixes #38, fixes #40
LibMagick: include support for setting compression
Merge branch 'io'

Conflicts:
	src/io.jl