Fix MIT extractor for Python 2.6

The HTML for the MIT page does not parse cleanly for Python 2.6 due
to script tags within an actual script element.  The offending piece
is inside a comment block, so removing all such comment blocks
fixes the parsing.
Fix detection of the webpage charset if it's declared using ' instead of "

Like in "<meta charset='utf-8'/>"
Also print the field that fails if it is a md5 checksum
Update descriptions checksum for some test for Unistra and Youtube
Merge pull request #1342 from whydoubt/fix_mit_26

Fix MIT extractor for Python 2.6
Add an extractor for orf.at (closes #1346)

Make find_xpath_attr also accept numbers in the value
Merge pull request #1 from rg3/master