Command line installer

Adds a php script that can be installed using curl. The install script will download the JS file directly from github and save it to the correct path. The install path can be changed using `--install-dir=<dir>`.

Adds a new route to the web app to serve above php file. I was unable to run `composer install` to test if route works, but I believe it should.

In production you can install using: `curl -sS http://papermodelplane.com/install | php`.