Require user to specify boxsize rather than automatically detect particle
extent in periodic theory boxes. Applies to Python, command line, and C API.
The order of some Python keyword args has also changed. [#199]

In the theoretical VPF calculation (theory.vpf), the total volume of the random spheres can now exceed the volume of the sample [#238]
Gridlink (the binning of particles into cells) now uses a parallel algorithm for the theory module [#239]
Add detection of known-bad Cray hugepages library at NERSC [#246]
Replace np.float with np.float64 to fix numpy 1.20 deprecation [#250]
Test Numpy versions as old as 1.14 and recent as 1.20 [#251]
Add lscpu and preprocessor defs to CI output [#259]

Fix Python reference leak to results struct [#229]
Fix parsing error when periodic=False and boxsize not given in the theory module [#257]