Merge branch 'feature/container_hash' of https://github.com/danieljames/type_traits into develop

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appveyor.yml

@@ -60,6 +60,7 @@ install:
   - git submodule update --init libs/type_index
   - git submodule update --init libs/utility
   - git submodule update --init libs/functional
+  - git submodule update --init libs/container_hash
   - xcopy /s /e /q %APPVEYOR_BUILD_FOLDER% libs\type_traits
   - bootstrap
   - b2 headers