Impossible to parse cyrillic Uri

**Issue by [RomanIakovlev](https://github.com/RomanIakovlev)**
_Tuesday Feb 02, 2016 at 19:17 GMT_
_Originally opened as https://github.com/akka/akka/issues/19677_

---

Consider this:

`"com.typesafe.akka" %% "akka-http-experimental" % "2.4.2-RC1"`

```
import akka.http.scaladsl.model.Uri

scala> Uri("http://президент.рф/", Uri.ParsingMode.Relaxed)
akka.http.scaladsl.model.IllegalUriException: Illegal URI reference: Invalid input 'п', expected 'EOI', '#', '?', path-abempty or authority (line 1, column 8): http://президент.рф/
^
at akka.http.scaladsl.model.IllegalUriException$.apply(ErrorInfo.scala:40)
at akka.http.scaladsl.model.Uri$.fail(Uri.scala:741)
at akka.http.impl.model.parser.UriParser.fail(UriParser.scala:62)
at akka.http.impl.model.parser.UriParser.parseUriReference(UriParser.scala:33)
at akka.http.scaladsl.model.Uri$.apply(Uri.scala:209)
at akka.http.scaladsl.model.Uri$.apply(Uri.scala:199)
... 43 elided

```

Any insights on how to tackle this?

Reproduce the failure through akka.http.scaladsl.model.Uri.apply with Uri.ParsingMode.Relaxed, then read akka.http.impl.model.parser.UriParser.scala and akka.http.scaladsl.model.Uri.scala around the reported stack frames. Done means the shown Cyrillic URI parses successfully without regressing existing URI parsing behavior; the issue does not name a test file.

Written by the indexing model from the issue text.