consistentize testing for and commenting on being a CommonJS module
don't start adb server until dashboard opens, and kill it when it closes
Merge branch 'master' into minimize-adb
kill ADB only on unload instead of every time the Dashboard closes

Ideally, we'd continue killing ADB every time the Dashboard closes.
But a new ADB service instance can't reconnect to a device to which
another instance previously connected until the device is replugged
into the computer or its adbd daemon is restarted.  So we're better
off leaving ADB running while the addon is loaded.
Merge pull request #406 from mykmelez/minimize-adb

start ADB lazily and kill it on unload