Added Cite to Arbitrary instance.

See #1269.  This reveals some test failures.

tests/Tests/Arbitrary.hs

@@ -64,6 +64,7 @@ arbInline n = frequency $ [ (60, liftM Str realString)
                               x3 <- realString
                               x2 <- liftM escapeURI realString
                               return $ Image x1 (x2,x3))
+                   , (2,  liftM2 Cite arbitrary (arbInlines 1))
                    , (2,  liftM Note $ resize 3 $ listOf1 $ arbBlock (n-1))
                    ]
 
@@ -111,7 +112,6 @@ instance Arbitrary Pandoc where
         arbitrary = resize 8 $ liftM normalize
                              $ liftM2 Pandoc arbitrary arbitrary
 
-{-
 instance Arbitrary CitationMode where
         arbitrary
           = do x <- choose (0 :: Int, 2)
@@ -123,14 +123,13 @@ instance Arbitrary CitationMode where
 
 instance Arbitrary Citation where
         arbitrary
-          = do x1 <- liftM (filter (`notElem` ",;]@ \t\n")) arbitrary
-               x2 <- arbitrary
-               x3 <- arbitrary
+          = do x1 <- listOf $ elements $ ['a'..'z'] ++ ['0'..'9'] ++ ['_']
+               x2 <- arbInlines 1
+               x3 <- arbInlines 1
                x4 <- arbitrary
                x5 <- arbitrary
                x6 <- arbitrary
                return (Citation x1 x2 x3 x4 x5 x6)
--}
 
 instance Arbitrary MathType where
         arbitrary