Handle runConfig.dir/modules scenario with multiple outputs

[dbashford]

Currently the messaging is entirely based on runConfig.out. But when using modules and building multiple files for a single run, there is no runConfig.out. Fix messaging.

Also, output reporting from r.js is different for multi-file outputs.

When using runConfig.out, r.js returns a text string report that can be used to detemine what files are used to build the r.js combined files.

When using runConfig.dir, r.js doesn't return anything, instead it writes a built.txt that contains that information. Need to read that, parse it, and allow for combined file removal.

See dbashford/mimosa#274

cc: @krokhale