Fix time datetime attribute

Should follow this syntax: year-month-day
Fix h1 use

W3C Validator says: "Consider using the h1 element as a top-level heading
only (all h1 elements are treated as top-level headings by many screen
readers and other tools)."
Remove unecessary meta tag to IE version
Fix header__about html element

The <section> should be used in places with a heading. <div> is the best
for this not so semantic block of text.