Consul config issues

[mjkoo]

Describe the bug Consul config module has some code smell and is breaking tests

• [x] Depends on environement variables being set, no fallback, everything else is in settings.rs (can set stuff from environment there with override)
• [ ] Returns bare Strings, .expects() and .unwraps() several times causing potential panics
• [x] eprintln! vs macros from log crate

Our test suite isn't great but the existing mock tests are broken by this

To Reproduce Steps to reproduce the behavior:

1. cargo test

[myhndl]

Do any of these issues block development or would you categorize this more as development velocity (see my email) items?

[mjkoo]

This blocks #18 which is a "velocity" item, but also could result in reliability issues in relay imo

[myhndl]

Not actually a blocker, per: https://github.com/polyswarm/relay/issues/18#issuecomment-438084006

[myhndl]

High priority per @mjkoo , moving up in column