HTML Cleanup

Moving from HTML Transitional to HTML5, there are some minor changes the way we write tags, elements etc..

1. Ending forward-slash is removed in `<img>`, `<br>` and `<link>`
2. Certain style specific attributes in html elements are now removed and moved into CSS code
     * `<center>` is removed and instead used CSS for it
     * `border` attr in `<img>` is removed and instead used CSS

These commits would improve code and don't change the way site is represented!