cloudcmd v3.1.0

fix

• (util) check: isEmpty

feature

• (package) checkup v1.3.0
• (cloudcmd) speedup: execon.series -> express
• (package) checkup v1.1.0
• (package) add checkup back
• (package) v1.1.0
• (package) rm checkup
• (package) gulp v3.9.0
• (listeners) DOM.toggleClass -> classList.toggleClass
• (bower) add domtokenlist-shim
• (util) exec.with: callback.bind -> bind.apply
• (util) exec.with: arguments[0] -> slice.call(arguments)
• (dom) rm addClass, removeClass
• (dom) loading, error: DOM.add/removeClass -> classList.add/remove
• (dom) Images.show.error: jqXHR -> text