Mostly by @gdooms, with tweaks.

- Also add tests for spacing in param names.

- Stop parsing new templates if the template depth gets above
  MAX_DEPTH (40) or if we've already tried to parse over MAX_CYCLES
  (100,000) templates.
- Add two tests to ensure recursion works somewhat correctly.
- Fix parsing the string "{{" with the Python tokenizer; add a test.

Update Pywikipedia documentation and links

Also, add a missing docstring in TreeEqualityTestCase.

- Add a _SliceNormalizerMixIn to properly handle slices.
- Use floor division when applying key.step.
- Implement sort() without 'cmp' parameter.
- Fix bytes(list) behavior.
- Children of _ListProxies are now _ListProxies, not regular lists.