major update to fix the issue of memory limitations for parallel compuation

The code now can handle extremely large number of pixels with parallel computation

SZpack library can be installed and imported correctly

The SZpack library can be imported in python2 and python3 without a problem.
But the implementation of this library is still missing.

correction on SPH smoothing for fine mesh

Problem with SPH smoothing: particles outside of the mesh grid leave a strong effect at the edge of the mesh grid.
It is solved with additional cut in the input particle data. Periodic boundary condition is also added into the cKDTree calculation for the mesh grid.

Theoretical y-map calculation done with parallel computation

This is a pre-release of the pymsz package.
This code currently works fine to generate the y-map for thermal S-Z effect.