Remove deprecated screen_icon() calls. Props netweb. Fixes #2538

git-svn-id: https://bbpress.svn.wordpress.org/trunk@5265 9866e705-20ec-0310-96e7-cbb4277adcfb
First pass at unit test suite. Props netweb. See #2542.

git-svn-id: https://bbpress.svn.wordpress.org/trunk@5266 9866e705-20ec-0310-96e7-cbb4277adcfb
Fix relative path to unit test bootstrap. See #2542.

git-svn-id: https://bbpress.svn.wordpress.org/trunk@5267 9866e705-20ec-0310-96e7-cbb4277adcfb