Rearrange & regroup EditorCommandHandler tests

This is for problem discussed here: https://groups.google.com/forum/?fromgroups#!topic/brackets-dev/1K6s_HWD06E

I move one of the "category: integration" group down to be next to the other "category: integration" group, and then wrapped a describe() block around all of them (unfortunately, the diff makes it look more complicated than that -- probably because of the indenting that was introduced).