IntervalIndex Comparisons of Signed / Unsigned
Compiling intervaltree.pxi.in yields 128 warnings in the build, most of which deal with the comparison of signed and unsigned data. 

These warnings add to the compile time, but also for sure highlight bugs like this:

```python
# Create an IntervalIndex using values only in the range of uint64
>>> ser = pd.Series([1], index=pd.IntervalIndex.from_tuples([((2 ** 63), (2 ** 64)-1)]))
# Negative value isn't in those ranges, but overflow yields undefined behavior
>>> ser[[-20]]
(9223372036854775808, 18446744073709551615]    1
dtype: int64
```

I think should probably separate unsigned vs signed parametrization