Abstract variables from deploy.sh

[n-hebert]

It would be good to have a .env file that could store some of the key variables.

I'm a bit of a BASH enthusiast, and I'm a big fan of this sort of default syntax where any good default exists:

export MYVAL=${MYVAL:-whatever}

If the user passes in an environment variable for MYVAL, it'll take it, but otherwise it's whatever.