move Currency to Ledger/

Amount.hs

@@ -38,7 +38,7 @@ module Amount
 where
 import Ledger.Utils
 import Ledger.Types
-import Currency
+import Ledger.Currency
 
 tests = runTestTT $ test [
          show (dollars 1)   ~?= "$1.00"

Ledger/Currency.hs

@@ -1,4 +1,4 @@
-module Currency
+module Ledger.Currency
 where
 import qualified Data.Map as Map
 import Data.Map ((!))