Intervaltree

-Bug fixes:
- `Node.depth_score_helper()` raised `AttributeError`
- README formatting

- Fix: pip install failure because of failure to generate README.rst

- Renamed from PyIntervalTree to intervaltree
- Speed improvements for adding and removing Intervals (~70% faster than 0.4)
- Bug fixes:
- BACKWARD INCOMPATIBLE: `len()` of an `Interval` is always 3, reverting to default behavior for `namedtuples`. In Python 3, `len` returning a non-integer raises an exception. Instead, use `Interval.length()`, which returns 0 for null intervals and `end - begin` otherwise. Also, if the `len() === 0`, then `not iv` is `True`.
- When inserting an `Interval` via `__setitem__` and improper parameters given, all errors were transformed to `IndexError`
- `split_overlaps` did not update the `boundary_table` counts
- Internal improvements:
- More robust local testing tools
- Long series of interdependent tests have been separated into sections

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- Fixed issue 5. This is the last version of this project.

- Faster balancing (~80% faster)
- Bug fixes:
- Double rotations were performed in place of a single rotation when presented an unbalanced Node with a balanced child.
- During single rotation, kept referencing an unrotated Node instead of the new, rotated one

- Made IntervalTree crash if inited with a null Interval (end <= begin)
- IntervalTree raises ValueError instead of AssertionError when a null Interval is inserted