* Refactoring:
- Expose class member functions to module level
- Rename member function of class Mole,
xxx_of_atm -> atom_xxx, xxx_of_bas -> bas_xxx
- Rename scf.hf.scf_cycle to scf.hf.kernel
- Rename conv_threshold to conv_tol
- Rename hf.calc_tot_elec_energy to hf.energy_tot
- Rename hf.set_mo_occ to hf.get_occ
- unify variable names, mo -> mo_coeff, log -> verbose
- Include nuclear repulsion in mcscf.e_tot
- Add tests for most module level functions
- Define update_casdm for CASSCF
* Add tests, cover ~ 90% of code
* Support molecular geometry string as input for Mole.atom
* Improve density fitting model for non-relativistic SCF
* Add documentation for whole package
* API updates:
- Remove the first argument (Mole object) in CASSCF/CASCI class initialization
- Change the return value ordering of function scf.hf.kernel
- Set default value for the arguments of most class functions
* Removing the default calling of analyze() in kernel functions
* Fix screening bug in ao2mo.outcore for long-range separated molecule
* Add 4pdm