Reviewed codes merged from ShawnFoo#6, corrected some code styles and…

… updated usages of APIs.

Added statment to filter empty messages' array from the Javascript side

1. fixed ShawnFoo#2(the error in webView:didFailLoadWithError: every …

…time the iframe's source changed)

2. change loadRequest: to loadHTMLString:baseURL:

Changed the code which its syntax will be modified in Swift3.0

update README