Integrate updated /history endpoint

[conlan]

yeah endTime and startTime and inclusive endTime is the latest time to include so you could either say, gimme transactions between these 2 timestamps (inclusive) or start at endTime (inclusive) and gimme X transactions before that that's intended for the endless transaction scrolling so when you first load an exchange it shows: tx1 <--- timestamp now tx2 tx3 tx4 tx5 (edited) then when you scroll to the bottom, call endTime = tx5.timestamp - 1, count = 5 and you'll get tx6 tx7 tx8 tx9 tx10