Downgrade imagemin to a more stable version

grunt-contrib-imagemin 0.5.0 randomly fails by throwing an error or generating empty images. gruntjs/grunt-contrib-imagemin#163
Merge pull request #312 from silvenon/patch-1

Downgrade imagemin to a more stable version
bower notes
Merge branch 'master' of https://github.com/yeoman/generator-webapp

Conflicts:
	app/templates/_package.json
	readme.md
re-apply fix
fixes from... yesterday :D
Merge branch 'master' of github.com:clemos/generator-haxe-webapp