We weren't storing annual epi_sizes after recent refactoring.
Getting ready for new ABC run

This time we're burning in for 100 years, followed by 20 years of no
epidemics, and then calculating metrics on the 35 years that follow.

20 year period corresponds to the erradication of dengue between the
50's and 70's, and then the 35 year period is for 1979-2013.
Forgot to throw out first 120 years of burnin in abc run