Change RUST_SRC_PATH check to look for /libstd under the first path. Fix for #253
Change RUST_SRC_PATH check to look for /libstd under the first path. Fix for #253

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