Write data out post-simulation instead of pre-simulation for out_interval years

When writing data to HDF store in out_interval years, write data post-simulation instead of pre-simulation.  This convention has the benefit that when you are looking at output for a given year, that year's control totals are met instead of previous year's control totals being met (as in the case when you write data out at the beginning of the simulation year).  

@jiffyclub Could you review this?
Looks like the unit tests are passing now, PEP8 just doesn't like 3 empty lines here, it wants 2.