Manifest checker: test for different_case earlier (see #119)

This ensures that the test won’t flag the file it just added
for any case where the filename isn’t already lowercased.

src/main/java/gov/loc/repository/bagit/conformance/ManifestChecker.java

@@ -123,9 +123,9 @@ private static void checkManifestPayload(final Path manifestFile, final Charset
         String path = parsePath(line);
 
         path = checkForManifestCreatedWithMD5SumTools(path, warnings, warningsToIgnore);
-        paths.add(path.toLowerCase());
-
         checkForDifferentCase(path, paths, manifestFile, warnings, warningsToIgnore);
+        paths.add(path.toLowerCase());
+
         if(encoding.name().startsWith("UTF")){
           checkNormalization(path, manifestFile.getParent(), warnings, warningsToIgnore);
         }