Added issuer to the transaction history grid

I think adding the column (Issuer) next to Amount will help users to understand one of the key concepts of Stellar: trust who is keeping the credit you own.

![screen shot 2014-08-05 at 11 26 32 am](https://cloud.githubusercontent.com/assets/428680/3816382/15e4e36a-1cce-11e4-8fdb-111f3b607d3d.png)

In case the issuer is NaN, it's defaulted to StellarFoundation.