[Proposal] Detect html5 <meta charset="">

[blaaat]

Currently only the http-equiv meta tag is used to find the charset used. I propose to include the html5 charset as well.

[shusaura85]

I added the meta charset detection. I'm not sure it's the best method but was the fastest.
I've attached the modified detectCharset() function from Dom.php here.
I added the detection for the meta charset as primary check and enclosed the original http-equiv check in the else branch

Dom.txt