Remove unused imports (with newer protolude)

The changes here are from fixing stack build with LTS 15.8 (GHC 8.8.3)
to be warning-free. Most if not all come from the newer protolude
version, which adds some things like `unwords`.

So to make sure that we don't get unused import warnings with newer
stackage, this both raises the protolude lower bound and removes
these imports.

main/Main.hs

@@ -17,8 +17,7 @@ import Data.IORef               (IORef, atomicWriteIORef, newIORef,
                                  readIORef)
 import Data.String              (IsString (..))
 import Data.Text                (pack, replace, strip, stripPrefix)
-import Data.Text.Encoding       (decodeUtf8, encodeUtf8)
-import Data.Text.IO             (hPutStrLn, readFile)
+import Data.Text.IO             (hPutStrLn)
 import Data.Time.Clock          (getCurrentTime)
 import Network.Wai.Handler.Warp (defaultSettings, runSettings,
                                  setHost, setPort, setServerName)