Automated testing of code examples in docs

It would be nice to have a Travis job that automatically extract complete code examples from the docs and confirms that they compile. It would also be nice if it checked that running the snippet produces expected output, if such output is provided in the text.

No files or tests are named. Start by locating the documentation examples and the existing Travis configuration, then determine how complete snippets and any expected output are identified. Done means CI compiles the extracted examples and verifies their stated output when available.

Written by the indexing model from the issue text.