Add price history to market outcomes

[scottzer0]

savvy traders will want price history and lovely graphs

[tinybike]

One option I've used before (and really liked) is Highstock. Eye-popping interactive price/candlestick/volume charts, requires very little work. If you're not already set on the corechart module (I'm not familiar with it so can't comment), I'd like to cast my vote in favor of using Highstock.

[joeykrug]

Implemented logs for this (market pricing):

event updatePrice(outcome, price)

log(type=updatePrice, outcome, MARKETS.price(market, outcome))

which is basically log(type=updatePrice, outcome, price)