Merge pull request #1 from toddfries/master

enhance module by providing user specified exchanges, do some refactoring, code deduplication
Version 0.1
permit TransHistory to work, update docs
+CancelOrder,+Trade; discover arg issue FIXME!!
clarify issue
rework _post with some inspiration from Finance::MtGox .. done in a much simpler and very different way so now args are properly signed and work!
Merge branch 'master' of github.com:toddfries/Finance-btce

Conflicts:
	lib/Finance/btce.pm