brew.rb: don't show help for 'brew <command> help'
brew.rb: don't show help for 'brew <command> help'

Showing help makes sense for `brew help <command>`, but showing it for
`brew <command> help` is undesirable and prevents all commands from
accepting a named argument `help` (formula, tap, file name, etc.).

All other help flags are still detected before *and* after the command.

Closes #103.

Signed-off-by: Martin Afanasjew <54669547a225ff20cba8b75a4adca540eef25858@afanasjew.de>

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