H edition

Hi, I have made some updates.
Lower the version to API 15, because 19 can not be test on my Android device, so I made this change.
Also , I add a function to shake to random visit a page.I think it is interesting,so hope it helps you.
Also, I add a guide activity, to teach how to use the app in the first time.
Well~~that is all , maybe add more in the future time.
By the way, use original webview seems a little bit slow, maybe need some optimizations there^ ,so I did not change any of that part