Support base as old as 4.9

SJW.cabal

@@ -26,7 +26,7 @@ library
                      , SJW.Module.Imports
                      , SJW.Source
   build-depends:       attoparsec
-                     , base >=4.11 && <4.13
+                     , base >=4.9 && <4.13
                      , containers
                      , directory
                      , filepath
@@ -42,7 +42,7 @@ executable sjw
   other-modules:       Paths_SJW
   -- other-extensions:
   build-depends:       attoparsec
-                     , base >=4.11 && <4.13
+                     , base >=4.9 && <4.13
                      , optparse-applicative
                      , SJW
                      , text

src/Main.hs

@@ -2,6 +2,7 @@
 module Main where
 
 import Control.Applicative (many, optional)
+import Data.Monoid ((<>))
 import qualified Data.Text as Text (unpack)
 import Data.Version (showVersion)
 import Options.Applicative (