smarter html recognition

[onurmatik]

First of all thanks for all the effort. I find this extension very handy.

Currently only if the message body starts with , the email is rendered as html. Although perfectly valid, if the html tag as extra attributes, such as , the email is rendered as plain text.

Also, if the document has , etc. as the first tag, it is rendered as plain text as well.

[ramusus]

fixed e2d90c4