Test improvements

[RebeccaMahany]

• Add flare to test and to artifacts
• Add mock k2 server for running tests against
• Gets desktop app running in test

[directionless]

I think this is (a) awesome work and (b) okay to merge, but I do have some nits around the mock server:

• It's not k2 it's a agent or launcher mock
• It should probably live in the launcher repo
• I feel very unsure about python.
• I kinda wonder about baking into launcher directly.

But anyhow, this is awesome.

[RebeccaMahany]

@directionless --

* It's not `k2` it's a `agent` or `launcher` mock

Fair -- I will update the name in the next PR. Maybe deviceserver?

* It should probably live in the launcher repo
* I feel very unsure about python. 
* I kinda wonder about baking into launcher directly.

This was just the fastest thing that I got going that actually worked, but I'm definitely happy to move it to golang, move it to another location, etc! I added a tracking item here: kolide/launcher#1532