fix url to logo in readme
fix url to logo in readme

douglaskastle/bootswatch,thomaspark/bootswatch,thomaspark/bootswatch,nkraft/bootswatch,nicolasmccurdy/bootswatch,douglaskastle/bootswatch,douglaskastle/bootswatch,nicolasmccurdy/bootswatch,nkraft/bootswatch,nkraft/bootswatch,douglaskastle/bootswatch,thomaspark/bootswatch,nicolasmccurdy/bootswatch