Simplified logging

[ejholmes]

Closes #527

This removes the "loop logger", and replaces it with a simple sequential logger. I think this solves all of the problems talked about in #527:

1. This will work with parallelized execution.
2. You get color output with --interactive.
3. It removes the superfluous "pending" status.
4. It scales easily with large stack configs.

Here's an example of what the output looks like:

[codecov-io]

Codecov Report

Merging #532 into master will decrease coverage by 0.65%.
The diff coverage is 46.42%.

@@            Coverage Diff             @@
##           master     #532      +/-   ##
==========================================
- Coverage    88.6%   87.94%   -0.66%     
==========================================
  Files          94       91       -3     
  Lines        5987     5875     -112     
==========================================
- Hits         5305     5167     -138     
- Misses        682      708      +26

Impacted Files	Coverage Δ
stacker/commands/stacker/__init__.py	95.83% <ø> (ø)	⬆️
stacker/context.py	97.22% <ø> (-0.04%)	⬇️
stacker/logger/__init__.py	0% <0%> (-100%)	⬇️
stacker/actions/base.py	63.79% <100%> (-1.79%)	⬇️
stacker/plan.py	90.8% <100%> (-0.78%)	⬇️
stacker/commands/stacker/base.py	84.28% <75%> (-1.43%)	⬇️

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[russellballestrini]

Wow, this is refreshing, nice work!

[phobologic]

love this, thanks.

[phobologic]

Ok, pushed a small update. @ejholmes can you take a look at why the test_util.py tests are all super noisy in tests now? See: https://circleci.com/gh/remind101/stacker/1404?utm_campaign=vcs-integration-link&utm_medium=referral&utm_source=github-build-link

(I thought it was something I had done, but it looks like it's been happening since this update)

[ejholmes]

Tests were noisy because the root logger in tests was being switched out with a StreamLogger in stacker/tests/test_stacker.py.

I added a commit to this that dependency injects the setup_logging function from scripts/stacker so unit tests can't fuck with logging.