Add config to skip mutagen dependency

[johnshaughnessy]

What

Add a config file (docker-compose-bind-mounts.yml) that can be merged with docker-compose.yml to avoid mutagen and mutagen-compose dependencies.

Why

Mutagen and mutagen-compose are especially useful on MacOS (and Windows?), where docker's bind mounts do not perform well, but don't seem necessary on linux.

The scripts in bin/ still call mutagen-compose, but I thought this would still be worth sharing for Linux users who may be familiar with docker but not mutagen.

[bryanenders]

This duplicates logic between files which could lead to skew down the road. For example, every change to bin/init will necessitate a change to docker-compose-init.yml and every change to docker-compose.yml will force a change to docker-compose-bind-mounts.yml and vice versa! I’m not sure that it’s worth it when the existing setup is already cross-compatible.

An alternative would be a note in the README on how to use bind mounts instead.

[johnshaughnessy]

Fair enough -- I'll close this in favor of keeping one cross-compatible config. We can revisit down the road if other users ask or look for ways to drop the mutagen dependency.