Support template-haskell and tests on GHC < 8.8 (#56)

We can effortlessly support GHC 8.0+ instead of GHC 8.8+ for both
building and testing, so let's do that.

GHC's before 8.8 (base-4.13) don't export `MonadFail` to Prelude.

Relax the bounds on `template-haskell` to support GHC 8.0+

Tighten the bounds on `containers` and `ansi-terminal` to exclude
unsupported versions.

Drop bounds specification in the test suite for dependencies shared with
the library; the library already constrains these dependencies and it
reduces maintenance burden.

Author: DigitalBrains1

System/Console/Docopt/Public.hs

@@ -1,3 +1,5 @@
+{-# LANGUAGE CPP #-}
+
 module System.Console.Docopt.Public
   (
     -- * Command line arguments parsers
@@ -42,6 +44,10 @@ module System.Console.Docopt.Public
 
 import System.Exit
 
+#if !MIN_VERSION_base(4,13,0)
+import Control.Monad.Fail (MonadFail)
+#endif
+
 import Data.Map as M hiding (null)
 import Data.Maybe (fromMaybe)
 import System.Console.Docopt.Types

docopt.cabal

@@ -45,7 +45,7 @@ library
 
   build-depends:      base >= 4.9 && < 5.0,
                       parsec >= 3.1.14 && < 3.2,
-                      containers >= 0.6.2 && < 0.7
+                      containers >= 0.6.2 && < 0.6.6
 
   ghc-options:        -Wall
                       -fno-warn-unused-binds
@@ -57,7 +57,7 @@ library
     exposed-modules:  System.Console.Docopt
     other-modules:    System.Console.Docopt.QQ
                       System.Console.Docopt.QQ.Instances
-    build-depends:    template-haskell >= 2.15.0 && < 2.18
+    build-depends:    template-haskell >= 2.11.0 && < 2.18
 
   default-language:   Haskell2010
 
@@ -74,17 +74,16 @@ test-suite tests
                       -fno-warn-orphans
 
   build-depends:      base,
-                      parsec >= 3.1.14 && < 3.2,
-                      containers >= 0.6.2 && < 0.7,
+                      parsec,
+                      containers,
                       docopt,
                       HUnit,
                       split,
-                      ansi-terminal,
+                      ansi-terminal >= 0.4,
                       aeson,
                       bytestring,
                       text,
-                      template-haskell >= 2.15.0 && < 2.18
-
+                      template-haskell >= 2.11.0 && < 2.18
 
   other-modules:      System.Console.Docopt
                       System.Console.Docopt.ApplicativeParsec