Remove unneeded logic introduced in a PR
Remove unneeded logic introduced in a PR

Closes #32

Should also fix #21 #31

Use dynamic mapping instead: https://github.com/gruntjs/grunt/wiki/Configuring-tasks#building-the-files-object-dynamically

vladikoff/grunt-contrib-imagemin,gruntjs/grunt-contrib-imagemin,bevacqua/grunt-contrib-imagemin,lstaszak/grunt-contrib-imagemin,guardian/grunt-contrib-imagemin