Files mapped to dev/tests by "required" composer packages

The composer.json file distributed with the application contains separate sections "require" and "require-dev" sections.
It is commonly expected that "require" section only contains dependencies necessary for production use, and not tests, tools used for development etc.

Preconditions

1. Magento 2.1.5 CE from https://magento.com/tech-resources/download

Steps to reproduce

1. Run "composer install --no-dev"

Expected result

1. No folder "dev/" in the application root or empty "dev" folder.

Actual result

1. Some files inside under dev/

To be precise, it is the magento2-base package maps quite a lot of its files into the dev folder, namely subfolders "dev/tools", "dev/travis" and "dev/tests/". These do not seem to be an integral part of the application itself, and as such must be separate into a package included inside the "require-dev" section of the composer. Accordingly, it would also be nice to see the "dev" folder added into the sample ".gitignore" file distributed with the package available from https://magento.com/tech-resources/download.

Start by inspecting the distributed composer.json and the magento2-base package mappings for dev/tools, dev/travis, and dev/tests. Run composer install --no-dev against Magento 2.1.5 CE to confirm which files are installed. Done means development files are excluded from the production install and the sample .gitignore accounts for the dev folder.