Add http2 support (#1)
Add http2 support (#1)

When using http2 module the `hostname` will be empty and there is a new pseudo-header field named `:authority`
According to RFC 7540 in https://tools.ietf.org/html/rfc7540#section-8.1.2.3
```
   o  The ":authority" pseudo-header field includes the authority
      portion of the target URI ([RFC3986], Section 3.2).  The authority
      MUST NOT include the deprecated "userinfo" subcomponent for "http"
      or "https" schemed URIs.
```
Equim-chan/koa-virtual-host