Clean up zsh completion
Clean up zsh completion

1. Fix a misspelled variable to avoid shell namespace pollution
2. Remove a bogus completion (the 'brew xo' one)
3. Add missing tab completion code for
   - Several arguments/commands (options, --cellar etc.)
   - Aliases (e.g. home and homepage)
   - 'brew edit' complete to all formulae, not just installed ones

Signed-off-by: Adam Vandenberg <34c2b6407fd5a10249a15d699d40f9ed1782e98c@gmail.com>

claui/brew,EricFromCanada/brew,hanxue/linuxbrew,muellermartin/dist,JCount/brew,toonetown/homebrew,konqui/brew,nandub/brew,pseudocody/brew,palxex/brew,rwhogg/brew,mahori/brew,aw1621107/brew,maxim-belkin/brew,ilovezfs/brew,Homebrew/brew,DomT4/brew,ilovezfs/brew,claui/brew,vitorgalvao/brew,sjackman/homebrew,jmsundar/brew,amar-laksh/brew_sudo,nandub/brew,EricFromCanada/brew,MikeMcQuaid/brew,konqui/brew,maxim-belkin/brew,vitorgalvao/brew,reitermarkus/brew,palxex/brew,hanxue/linuxbrew,mistydemeo/homebrew,aw1621107/brew,alyssais/brew,AnastasiaSulyagina/brew,MikeMcQuaid/brew,MikeMcQuaid/brew,jmsundar/brew,alyssais/brew,gordonmcshane/homebrew,EricFromCanada/brew,sjackman/homebrew,Linuxbrew/brew,palxex/brew,zmwangx/brew,amar-laksh/brew_sudo,gregory-nisbet/brew,zmwangx/brew,DomT4/brew,pseudocody/brew,DomT4/brew,rwhogg/brew,bfontaine/brew,Linuxbrew/brew,Homebrew/brew,Homebrew/brew,staticfloat/brew,JCount/brew,mahori/brew,konqui/brew,amar-laksh/brew_sudo,mgrimes/brew,aw1621107/brew,rwhogg/brew,reitermarkus/brew,toonetown/homebrew,mahori/brew,reelsense/brew,bfontaine/brew,ilovezfs/brew,claui/brew,JCount/brew,staticfloat/brew,reitermarkus/brew,muellermartin/dist,MikeMcQuaid/brew,mahori/brew,nandub/brew,EricFromCanada/brew,zmwangx/brew,mgrimes/brew,claui/brew,staticfloat/brew,mistydemeo/homebrew,jmsundar/brew,reelsense/brew,gregory-nisbet/brew,mistydemeo/homebrew,tonyg/homebrew,AnastasiaSulyagina/brew,pseudocody/brew,Homebrew/brew,AnastasiaSulyagina/brew,vitorgalvao/brew,Linuxbrew/brew,tonyg/homebrew,reitermarkus/brew,mgrimes/brew,bfontaine/brew,reelsense/brew,sjackman/homebrew,JCount/brew,muellermartin/dist,toonetown/homebrew,sjackman/homebrew,alyssais/brew,tonyg/homebrew,gregory-nisbet/brew,maxim-belkin/brew,Linuxbrew/brew,vitorgalvao/brew,gordonmcshane/homebrew,nandub/brew,DomT4/brew,gordonmcshane/homebrew,konqui/brew,hanxue/linuxbrew