crypto-square: Check whitespace

Fixes exercism#895, the complaint that
the whitespace was being ignored.

The canonical test data itself is fine; the problem was that the test
suite was ignoring whitespace when comparing the actual result to the
expected result.

The decision to ignore whitespace was a originally deliberate decision,
with the reasoning in exercism#259.

However, maintainers' current judgment is that as long as our output is
a String, it's better to keep it as the problem description says, for it
would be against the description if a student emitted an output with a
lot of leading spaces (among others).

If the track changes the output to a [String], then the maintainers
could freely choose whether to require the trailing spaces or forbid
them.

exercises/practice/crypto-square/examples/success-standard/src/CryptoSquare.hs

@@ -6,10 +6,15 @@ import Data.List.Split (chunksOf)
 
 encode :: String -> String
 encode = unwords
+       . justify
        . transpose
        . (squareSize >>= chunksOf)
        . map toLower
        . filter isAlphaNum
   where
     squareSize :: String -> Int
     squareSize = ceiling . (sqrt :: Double -> Double) . fromIntegral . length
+    justify :: [String] -> [String]
+    justify [] = []
+    justify (x:xs) = let width = length x in
+                         x : map (\s -> take width (s ++ repeat ' ')) xs

exercises/practice/crypto-square/test/Tests.hs

@@ -17,13 +17,12 @@ specs = describe "encode" $ for_ cases test
 
     test Case{..} = describe description $ do
 
-      let shouldMatchWords  = shouldBe        `on` words
-          shouldMatchString = shouldBe        `on` filter (not . isSpace)
+      let shouldMatchString = shouldBe        `on` filter (not . isSpace)
           shouldMatchChars  = shouldMatchList `on` filter (not . isSpace)
 
       it "normalizes the input"    $ encode input `shouldMatchChars`  expected
       it "reorders the characters" $ encode input `shouldMatchString` expected
-      it "groups the output"       $ encode input `shouldMatchWords`  expected
+      it "groups the output"       $ encode input `shouldBe`          expected
 
 data Case = Case { description :: String
                  , input       :: String