Support -f on torus set

[ianlivingstone]

Many times, secrets are stored in a file, it'd be nice if you could import secrets from a file into torus using the set command.

Something like:

$ torus set -e myprod -f secrets.yml

Where the supported files are yaml, json, or env

[jbowes]

This makes more sense as torus import to me.

[ianlivingstone]

For the short term, we just discussed having this be done by reading from stdin for key=value\n. Allowing you to pipe a env file (e.g.torus set -e prod < mysecrets)