create standard startup / rc script

[progrium]

Right now we initiate /root with a .bashrc script. We use this to register aliases for envy commands and soon to source in any startup scripts/profiles in the owner's home directory.

Problem is .bashrc is not sourced with distros that just have a posix shell like Alpine. Posix doesn't define startup files that it sources by default, but it does source whatever file is defined in an ENV variable. I think we should standardize this to load /root/.envrc. We should put anything Envy related here, and then have .bashrc source it in cases where bash is used instead of sh.

In case anybody is curious about the "rc" naming convention: http://unix.stackexchange.com/questions/3467/what-does-rc-in-bashrc-stand-for

[progrium]

Although a little different than documented here, this commit resolves this and is now documented in the readme: 88f3ef6