shell: add `gvim` and `mvim` aliases

Alias these commands so that they always open files in an existing
MacVim window, rather than spawning a new window.
shell: add `gvim` and `mvim` aliases

Alias these commands so that they always open files in an existing
MacVim window, rather than spawning a new window.
Merge branch 'master' of https://github.com/necolas/dotfiles