Update style.css.

Remove overqualified elements and move inline style to the css.
Fix validation errors.

Also add image dimensions and remove trailing spaces.
index.html: reindent to improve readability.
Trailing spaces.
Specify type and dimensions for the open graph image.
Losslessly compress images.
Refactor files in a more standard way.
Update README.md.

Use a direct link to license and use the https link for the website.