Add ATOM_REPOS_HOME for Atom package development
Add ATOM_REPOS_HOME for Atom package development

The command to fork an Atom package is `apm develop [package]`. This
clones the repository into the path pointed to by the `ATOM_REPOS_HOME`
environment variable and symlinks it into the `~/.atom/dev/packages`
directory.

lee-dohm/dotfiles,lee-dohm/dotfiles,lee-dohm/dotfiles,lee-dohm/dotfiles