very small things
Starting a nn branch
lj force is implemented
Improved -- hopefully --  program
Merge branch 'master' of https://github.com/akandra/md_tian

Conflicts:
	atom_class.f90
	fit4_tian.f90
	force.f90
	md_init.f90
	md_tian.f90
	md_tian_fit.inp
	model.f90
	output.f90