Added isHexadecimal to Readme
Added isHexadecimal to Readme

ycms/Stringy,danielkesselberg/Stringy,voku/Stringy,Big-Shark/Stringy,sofyansitorus/Stringy,marktopper/Stringy,ihsanudin/Stringy,wallacesilva/Stringy,takobell/Stringy,TCB13/Stringy,bocharsky-bw/Stringy,danielstjules/Stringy,lucasmichot/Stringy,taohaoge/Stringy