Scrolls and Potions oh my

Now that the first tranche of scrolls have been implemented, and my exams are finally over for the year, the next thing to add to the game are potions. Potions are slightly more complicated to implement than scrolls, given that scrolls are one-off effects and potions have effects over time. A while back, I listed the various types of potions I'd like to implement, but as with scrolls, I'll probably only implement a subset of these at first, and add more in later. I will release 0.0.5c when I have potions implemented.