Disable flag before release. Refs #203.

The internal-core flag exposes Yampa's internals. This kind of facility
is discouraged and rejected by hackage.

This commit removes that flag altogether before the upload to hackage.

yampa/Yampa.cabal

@@ -73,24 +73,6 @@ flag examples
   default:     False
   manual:      True
 
--- WARNING: The following flag exposes Yampa's core. You should avoid using
--- this at all. The only reason to expose it is that we are using Yampa for
--- research, and many extensions require that we expose the constructors. No
--- released project should depend on this. In general, you should always
--- install Yampa with this flag disabled.
-flag expose-core
-  description:
-    You can enable exposing some of Yampa's core constructs using
-    -fexpose-core.
-    .
-    Enabling this is an unsupported configuration, but it may be useful if you
-    are building an extension of Yampa for research and do not wish to fork
-    Yampa completely.
-    .
-    No released project should ever depend on this.
-  default: False
-  manual:  True
-
 
 library
   exposed-modules:
@@ -114,6 +96,7 @@ library
   other-modules:
     -- Auxiliary (commonly used) types
     FRP.Yampa.Diagnostics
+    FRP.Yampa.InternalCore
 
   build-depends:
       base < 6
@@ -134,13 +117,6 @@ library
     build-depends:
       fail == 4.9.*
 
-  if flag(expose-core)
-    exposed-modules:
-      FRP.Yampa.InternalCore
-  else
-    other-modules:
-      FRP.Yampa.InternalCore
-
 
 test-suite hlint
   type: