Fix all hlint warnings

- Html.hs: replace lambdas with section/composition where possible
- Html.hs: replace case/fromMaybe with fromMaybe
- Html.hs: add fromMaybe to imports, use unqualified
- Parser.hs: replace span with break (2 locations)
- Parser.hs: replace if/then/else with list comprehension
- Parser.hs: remove redundant catch-all patterns (break is exhaustive)
- Server.hs: eta reduce htmlResponse
- Add .hlint.yaml to suppress 'Avoid lambda' (suggested fix has
  precedence issues with blaze-html's infix (!) operator)
- All 26 tests passing, hlint: No hints, exit code 0

src/Roux/Server.hs

@@ -68,11 +68,10 @@ urlDecodePath = Html.urlDecode
 
 -- | Build a 200 HTML response.
 htmlResponse :: ByteString -> Wai.Response
-htmlResponse body =
+htmlResponse =
     Wai.responseLBS
         HTTP.status200
         [("Content-Type", "text/html; charset=utf-8")]
-        body
 
 -- | 404 response.
 notFound :: Wai.Response