Multiple Recompilation

With a large set of files, running brunch watch will initially say that it "compiled" in a small number of ms, and then continually compile an unspecified number of times before it finally finishes compiling everything.

I tracked this down to the fact that files that have dependencies compile those, and if they're still compiling, it creates this type of compile loop. By keeping track of what files are compiling, and then knowing when they're finished compiling, we can avoid recompiling the same files multiple times.