utils: convert formula name from pathname to string
utils: convert formula name from pathname to string

`name` is passed as argument to Formulary.factory which could later be
downcased at formulary.rb:349, but Pathname doesn't have a downcase
method. Converting `name` to String as it should be fixes the problem.

Fixes #1000.

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