UNI/HTML/WIP: add encoding argument to read_html
closes #7220

@klonuo would you like to try out this branch on your data and see if it's to your liking?
 don't you have to: cc @klonuo ?
 i did
 @cpcloud I just tried it and it works fine

Thanks for your patience
 great! thanks for the report. keep the issues coming . promise i won't bite anymore :)
 @jreback going to merge this after whatsnew
 yep
