Add -Werror, fix unused import warnings

- Add -Werror to ghc-options for both library and test suite
- Remove unused Data.Maybe import from Internal.hs
- Remove unused Data.Int and Data.Text imports from test files

orville-sqlite.cabal

@@ -34,7 +34,7 @@ library
     , text
     , bytestring
   default-language: Haskell2010
-  ghc-options: -Wall
+  ghc-options: -Wall -Werror
 
 test-suite spec
   type: exitcode-stdio-1.0
@@ -56,3 +56,4 @@ test-suite spec
     , hspec
     , text
   default-language: Haskell2010
+  ghc-options: -Wall -Werror