[#195] Allow doctest-0.17 (#196)

Resolves #195

Author: vrom911

co-log-core/co-log-core.cabal

@@ -91,5 +91,5 @@ test-suite doctest
   type:                 exitcode-stdio-1.0
   hs-source-dirs:       test
   main-is:              Doctests.hs
-  build-depends:        doctest ^>= 0.16.0
+  build-depends:        doctest >= 0.16.0 && < 0.18
                       , Glob ^>= 0.10.0