Rename IsObservable to Observable

src/lib/Qd/Observable.hs

 module Qd.Observable (
   SomeObservable(..),
-  IsObservable(..),
+  Observable(..),
   subscribe',
   SubscriptionHandle(..),
   Callback,
@@ -36,20 +36,20 @@ mapObservableMessage f (r, s) = (r, ) <$> mapObservableState f s
 
 newtype SubscriptionHandle = SubscriptionHandle { unsubscribe :: IO () }
 
-class IsObservable v o | o -> v where
+class Observable v o | o -> v where
   getValue :: o -> IO (ObservableState v)
   subscribe :: o -> (ObservableMessage v -> IO ()) -> IO SubscriptionHandle
   mapObservable :: (v -> IO a) -> o -> SomeObservable a
   mapObservable f = SomeObservable . MappedObservable f
 
-subscribe' :: IsObservable v o => o -> (SubscriptionHandle -> ObservableMessage v -> IO ()) -> IO SubscriptionHandle
+subscribe' :: Observable v o => o -> (SubscriptionHandle -> ObservableMessage v -> IO ()) -> IO SubscriptionHandle
 subscribe' observable callback = mfix $ \subscription -> subscribe observable (callback subscription)
 
 type Callback v = ObservableMessage v -> IO ()
 
 -- | Existential quantification wrapper for the Observable type class.
-data SomeObservable v = forall o. IsObservable v o => SomeObservable o
-instance IsObservable v (SomeObservable v) where
+data SomeObservable v = forall o. Observable v o => SomeObservable o
+instance Observable v (SomeObservable v) where
   getValue (SomeObservable o) = getValue o
   subscribe (SomeObservable o) = subscribe o
   mapObservable f (SomeObservable o) = mapObservable f o
@@ -57,15 +57,15 @@ instance IsObservable v (SomeObservable v) where
 instance Functor SomeObservable where
   fmap f = mapObservable (return . f)
 
-data MappedObservable b = forall a o. IsObservable a o => MappedObservable (a -> IO b) o
-instance IsObservable v (MappedObservable v) where
+data MappedObservable b = forall a o. Observable a o => MappedObservable (a -> IO b) o
+instance Observable v (MappedObservable v) where
   getValue (MappedObservable f observable) = mapObservableState f =<< getValue observable
   subscribe (MappedObservable f observable) callback = subscribe observable (callback <=< mapObservableMessage f)
   mapObservable f1 (MappedObservable f2 upstream) = SomeObservable $ MappedObservable (f1 <=< f2) upstream
 
 
 newtype BasicObservable v = BasicObservable (MVar (ObservableState v, HM.HashMap Unique (Callback v)))
-instance IsObservable v (BasicObservable v) where
+instance Observable v (BasicObservable v) where
   getValue (BasicObservable mvar) = fst <$> readMVar mvar
   subscribe (BasicObservable mvar) callback = do
     key <- newUnique