fix scroll issue in IE

[laysent]

Docify is not able to scroll to anchor in IE. This issue can be reproduced by using IE (for example IE 11) to visit docsify website and clicking link on sidebar.

According to MDN, property scrollY is not available in IE. Meanwhile, pageYOffset property is an alias for the scrollY property and is available in IE 9+ and all other browsers (details here).

The other commit will add extra meta tag in html files, to force IE browsers to render page using latest version of IE available. Otherwise, it might use IE 7 to render, which will cause issues.

Please makes sure these boxes are checked before submitting your PR, thank you!

• Make sure you are merging your commits to master branch.
• Add some descriptions and refer relative issues for you PR.
• DO NOT include files inside lib directory.