We must avoid the following features:
- the `using` syntax for typedefs
- alias templates (so, rename `hyper_function` to `function`)
- the `override` keyword
- defaulted virtual destructors
For testing the emscripten build in TravisCI, it looks like some
arcane combination of node + Browserify + the wasmify plugin + maybe
some other stuff *might* work, but I have no real idea yet.
For grabbing the build artifacts from Travis, you can temporarily
insert lines into the .travis.yml such as
curl --upload-file ./hyper.html https://transfer.sh/hyper.html
curl --upload-file ./hyper.js https://transfer.sh/hyper.js
curl --upload-file ./hyper.wasm https://transfer.sh/hyper.wasm
However, "hyper.wasm" is about 2.8 megabytes in size, so this hack
definitely should never become part of the *master* `.travis.yml`.
