Add load autoprefixer and cssmin

I may be missing something obvious here but grunt returns errors because cssmin and autoprefixer aren't being loaded. This seems to fix the problem.
Merge pull request #5031 from gpspake/patch-1

Add load autoprefixer and cssmin
Delete comma, add semicolon

Line 10 -> delete comma,
Line 55 -> add semicolon
Merge pull request #5076 from OliverKK/patch-1

Delete comma, add semicolon