Update to new bumped version of ImageMagick

new bumped version of ImageMagick according to http://www.imagemagick.org/download/binaries/
Merge pull request #218 from cmey/master

Update to new bumped version of ImageMagick
Add reassurance about missing property warning
Add a missing boundscheck
By default use a minimum # of pixels in writemime (fixes #220)

Also cleans up the writemime interface a bit.
Add test/REQUIRE, ensure test files run independently