Pushstate routing in `--static` mode

Pushstate routing is now handled automatically when SSR is turned off using the --static option. Static files are still first priority. If a static file doesn't exist for a URL, and the request is pushstate compatible (meaning it isn't for a file with an extension or might contain the ? character) an .html file based on the current environment will be loaded.

Environment Selection

DoneJS applications come with a development.html file and a production.html file in the project root. With any environment other than development, it will first attempt to find an .html file named after the current environment (process.env.NODE_ENV). For example, if the current NODE_ENV is qa, the server will check if qa.html exists. If it does, qa.html will be served. If not, the server will check for and load production.html.

If no .html file exists for the current environment, and there's no production.html, the request will return a 404.

PR: #30