The way that the config was loaded was pretty ugly--we had two closely

related structs, one of which was the serializable version, and one of

which was exactly the same except instead of the serialized repository

data, included Repository instances. This meant that adding any fields

involved adding it in multiple places and copying it back and forth.
This change merges those two, so that we load the data directly into the

struct and then instantiate Repository instances later.
I've also changed the testing to remove the ability to write out a

config. We had been testing loading the config by first generating a

Config struct and writing it to disk, then reading it back in and

comparing. This was the only place that serialized the config, and made

the test less isolated because it relied on both the serialization and

deserialization to work correctly. I've changed this so that we just

write out a JSON blob and then test that it can load correctly.

Ran unit tests.
Built and ran rb-gateway.