Subsite countly

This is related to Issue #19 as I wanted to try out countly on my VPS without getting another domain name.

Here's the nginx config I used:

```
server {
        listen   80;
        server_name  127.0.0.1;

        access_log  off;

        location = /ct/i {
                rewrite /ct/(.*) /$1 break;
                proxy_pass http://127.0.0.1:3001;
                proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
                proxy_set_header X-Real-IP $remote_addr;
        }

        location = /ct/o {
                rewrite /ct/(.*) /$1 break;
                proxy_pass http://127.0.0.1:3001;
        }

        location /ct/ {
                rewrite /ct/(.*) /$1 break;
                proxy_pass http://127.0.0.1:6001;
                proxy_set_header Host $http_host;
        }
}
```

Notice the rewrites make countly believe it's a root app. Most of the work was rewiring the html, css, js and images to play nice with <base>. I didn't thoroughly test this patch, but I did find that prefixfree has a bug which breaks some CSS https://github.com/LeaVerou/prefixfree/issues/134 and other than that it works for me.