Allow sensitive information to be declared in env.

Allow OAuth keys/passwords/other sensitive info to be loaded through the
environment instead of requiring them in the file.
Change email settings names.

Change from "email-" to "smtp-". Add from-name, from-address, username,
host, use_ssl to values picked up from env.
Merge pull request #33 from iamthechad/config_update

Allow sensitive information to be declared in env.