Renaming doc files to make the file names more palatable and in preparation for including documentation in sync process

googlemock/src/gmock-spec-builders.cc

@@ -292,7 +292,7 @@ void ReportUninterestingCall(CallReaction reaction, const std::string& msg) {
               "an EXPECT_CALL() if you don't mean to enforce the call.  "
               "See "
               "https://github.com/google/googletest/blob/master/googlemock/"
-              "docs/CookBook.md#"
+              "docs/cook_book.md#"
               "knowing-when-to-expect for details.\n",
           stack_frames_to_skip);
       break;