Changing trade.streaming.BTCChinaBalance.toString() method to be prettier.

Before, the method printed out a nasty string that prefixed the entire package name like:
com.xeiam.xchange...streaming.BTCChinaBalance@7f374, which is not a useful string.  The method is
now changed to behave like the toString() method in BTCChinaOrder of the same package.
Merge branch 'toStringRequest' of https://github.com/bryan4887/XChange into toStringRequest

Conflicts:
	xchange-btcchina/src/main/java/com/xeiam/xchange/btcchina/dto/trade/streaming/BTCChinaBalance.java