Remove private clone of Function#bind for old browsers (please use es5-shim).
Remove private clone of Function#bind for old browsers (please use es5-shim).

twada/power-assert-runtime,power-assert-js/empower,twada/empower-core,jamestalmage/empower-assert,power-assert-js/empower,twada/empower-core,jamestalmage/empower-assert