EUPS packaged version of Mike Jarvis' TreeCorr

https://github.com/rmjarvis/TreeCorr/archive/v3.2.3.tar.gz

Explanatory Notes

2017-07-27: Michael Wood-Vasey

1. We have specifically pinned to the 3.2.3 version to avoid the libffi, cffi, pyfits dependencies introduced in more recent versions. These dependencies make sense for TreeCorr qua TreeCorr, but add dependencies to the LSST validate_drp stack that we wish to avoid for now.

• In the future we may update. libffi and cffi should be set up as shim packages, particularly because libffi is available on many systems. The pyfits dependency we would have to step around because we do wish to avoid adding a 3rd (4th?) different python FITS interface to the LSST stack.
• For more discussion see https://jira.lsstcorp.org/browse/RFC-296
• If performance becomes an issue, we may want to update to more recent TreeCorr. But currently basic I/O from the catalog files dominates any in-memory correlation calculations. Thus until it becomes a performance bottleneck, I judge that the dependency minimization is the better option for the LSST validate_drp stack.

2. pandas could be a setupOptional dependency. If pandas is not present, then reading of ASCII catalogs will be slower. But we don't use that functionality, so I've left pandas out as a dependency.