Mixing binary and text types causes errors later on.

Use sorted() instead, which works on lists as well as dict_items
objects.

On Python 2, html_quote(unicode) returns again bytes to restore backward
compatibility.

* Remove unused variables
* Remove unused imports
* Remove dead code

Rename duplicated uninstall() function to uninstall_stdin() and fix typo in
variable name (_oldstin => _oldstdin).

Use self.pos instead of an unknown pos variable.