Add weather, define, and epoch functions to shared_env.d
Add weather, define, and epoch functions to shared_env.d

These are three useful functions found via quora:

http://www.quora.com/What-are-some-of-the-best-command-prompt-or-the-terminal-tricks

Before committing they were slightly modified for clarity and
consistency with the rest of the files.

alphabetum/dotfiles,alphabetum/dotfiles,alphabetum/dotfiles,alphabetum/dotfiles