Add tests for TopoJSON files (`.topojson`)

Add tests to check if `.topojson` files:

 * are serve compressed and with the `application/json` media
   type (there isn't yet and official or recommended media type)

 * aren't served with any of the `HTML` document related headers,
   aren't cached, and their specified character encoding is `UTF-8`

Ref: https://github.com/topojson/topojson-specification
     h5bp/server-configs-apache#34
Update `CHANGELOG.md`
v0.3.0