get PyCCS working with macs

[stevenqie]

on macs the binaries need to compile to a .dylib not a .so file. we had issues with this in charm4py but we still need to fix this in pyccs.

Current problem: When trying to run python3 -m pip install --user . it gives a libccs-client.so not found error

[ritvikrao]

pr for this is #6