Download Helper tests print log to screen

[sabjorn]

Even though:

// Prevent Logger output during tests
sandbox.stub(dh, "log");

is set in the tests, the logger still prints to screen when running tests

[emcniece]

I recall messing around with this to properly silence the logger. winston and its dependencies accounts for a significant portion of the bundle, and it's annoying to fight through this silencing - I propose we remove Winston and implement a very basic logging class ourselves.