Milestone improvements

Addresses #268 partially while Yuval completes mockups for pending orders page
![selection_114](https://cloud.githubusercontent.com/assets/2230604/2553987/a9f45394-b6ab-11e3-9095-edbf078c9b59.png)

*Adds block time limit to trade page
*update offers/address endpoint to use arrays as input
*Move trade offers history to pending offers page
*add hash explorer to explorer overview and history pages
*route to /overview in header by default
*New front end sorting for Sell/Buy offers on Pending page