API should close connection by default

[artgo]

To close connection we require our customers to explicitly do it via "Connection" header like so:

curl -i http://localhost:3000/api/override-default-heade  -H "Connection: close"

This is not a standard expected behaviour and creates unnecessary additional load on the servers

[artgo]

@kahmali FYI

[vadkasevas]

https://github.com/kahmali/meteor-restivus/blob/b95f879c0ebc52e0a7cd85e91fbc8ba5118026eb/lib/iron-router-error-to-response.js#L24