add function for HG_1to3_decay class and parameter reader
add all the functions, need to be tested
test passed
Merge branch 'master' of https://github.com/chunshen1987/viscous_emissionrate_tables_HG_rho_decay_with_chemical_potential_and_Formfactor into gsl_integration
categorize functions into classes
some clean ups and fixes
Merge branch 'fixedPiontsGaussIntegrations'