Schedule changes

This picks up a symposion change from the pyconca symposion branch that should help with staggered schedule display for #127. I've also checked csv files since maintaining htem in google docs is one of the most annoying things ever.

Once this is ready to go, I'll need to do 
`alter table schedule_slotkind add presentation bool not null default 1;`
on the db.

I've done this on staging already and regenerated the grid. example: https://citationsneeded.org/scipy2014/schedule/talks-posters/