Optimise mystery-man images with latest version of imagemin

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8486 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Grunt: Update phpunit grunt task to not use deprecated util

Fixes #5627, props netweb

git-svn-id: https://buddypress.svn.wordpress.org/trunk@8487 cdf35c40-ae34-48e0-9cc9-0c9da1808c22