Support modifying environment variables

[n0n0x]

12 factor apps like podcast api use a .env file, add a way to modify such files such as:

fab production set_env:ENV_VAR,ENV_VALUE

if the env exists, then replace if not, then append. http://docs.fabfile.org/en/1.11/api/contrib/files.html

Something like this should work:

if fabric.contrib.files.contains().failed:
    fabric.contrib.files.append()
else:
    fabric.contrib.files.sed()

maybe use if fabric.contrib.files.sed().failed: directly

[n0n0x]

https://github.com/theskumar/python-dotenv