Rtree

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0.5.0 was a complete refactoring to use libsidx - a C API for libspatialindex.
The code is now ctypes over libsidx, and a number of new features are now
available as a result of this refactoring.

* ability to store pickles within the index (clustered index)
* ability to use custom extension names for disk-based indexes
* ability to modify many index parameters at instantiation time
* storage of point data reduced by a factor of 4
* bulk loading of indexes at instantiation time
* ability to quickly return the bounds of the entire index
* ability to return the bounds of index entries
* much better windows support
* libspatialindex 1.4.0 required.

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- Fix reference counting leak 181

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- Windows support

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- Eliminate uncounted references in add, delete, nearestNeighbor (157).

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- Testing improvements.
- Switch dependency to the single consolidated spatialindex library (1.3).

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- Change to Python long integer identifiers (126).
- Allow deletion of objects from indexes.
- Reraise index query errors as Python exceptions.
- Improved persistence.