Make the citeproc-test runner Python 2 compatible

Also includes some other improvements
PyScripter's debug output doesn't have a close function
Restore proper behavior of MixedString addition

__class__ is not the same as self.__class__!
Fixes locale_TitleCaseGarbageLangEmptyLocale and
textcase_TitleCaseNonEnglish2
Some entries should not be parsed as a MixedString
More Python 2 (unicode/str) compatibility fixes

Fixes remaining testcases that did pass in Python 3 and gets rid of ascii
encode errors.

Prefer overriding str to yield cleaner code
Update README with news about Python 2.x compatibility and link to the CSL
website.
NF: add restructured text formatter
NF: add hairy script to output bibliography

Well - it's just an example