Add route returning JSON

---

• lib/D2/Ajax.pm

get '/' => sub {
    template 'index';
};

snippets/1/lib/D2/Ajax.pm

get '/api/v1/greeting' => sub {
    header 'Content-Type' => 'application/json';
    return to_json { text => 'Hello World' };
};

• http://127.0.0.1:5000/api/v1/greeting
• curl http://127.0.0.1:5000/api/v1/greeting

{"text":"Hello World"}

• curl -I http://127.0.0.1:5000/api/v1/greeting

HTTP/1.0 200 OK
Date: Mon, 24 Aug 2015 14:21:11 GMT
Server: HTTP::Server::PSGI
Server: Perl Dancer2 0.161000
Content-Type: application/json
Content-Length: 22