Changed PolyaGamma*.hpp to PolyaGamma*.h.
Changed LogitWrapper.hpp to LogitWrapper.h
Changed sync.bash to use .h files instead of .hpp files.
Fixed bug in calculating second moments in PolyaGamma.cpp
Added files for parallel hybrid sampler.
Changed Makefile to compile parallel hybrid sampler.
Changed includes to work with .h and adjusted indentation in some files.
Minor clarification in INSTALL file.
Removed old instructions in INSTALL file.
Fix moment calculations for negative c in PG(b, c)

Closes #7