Add some support for multirust
Add some support for multirust

 - if there's no .cargo directory, use the multirust default cargo directory
    ( e.g. ~/.multirust/toolchains/stable/cargo/ if default is 'stable')

rranelli/racer,phildawes/racer,asantopietro/racer,ajroetker/racer,ifraixedes/racer,BonsaiDen/racer,ajroetker/racer,syhkiller/racer,pmarcelll/racer,MattWis/racer,sliz1/racer,kbknapp/racer,MattWis/racer,BonsaiDen/racer,drewet/racer,ane/racer,ane/racer,racer-rust/racer,alkama/racer,jaxx/racer,drewet/racer,syohex/racer,kbknapp/racer,ifraixedes/racer,syhkiller/racer,sthapaun/racer,sthapaun/racer,asantopietro/racer,dleslie/racer,bluss/racer,bluss/racer,Wilfred/racer,hotpxl/racer,syohex/racer,rranelli/racer,birkenfeld/racer