feat(lib): remove extern Url type usage

BREAKING CHANGE: The `Url` type is no longer used. Any instance in the
  `Client` API has had it replaced with `hyper::Uri`.

  This also means `Error::Uri` has changed types to
  `hyper::error::UriError`.

  The type `hyper::header::parsing::HTTP_VALUE` has been made private,
  as an implementation detail. The function `http_percent_encoding`
  should be used instead.

src/http/h1/parse.rs

@@ -61,7 +61,7 @@ impl Http1Transaction for ServerTransaction {
         let path = unsafe { ByteStr::from_utf8_unchecked(path) };
         let subject = RequestLine(
             method,
-            try!(::uri::from_mem_str(path)),
+            try!(::uri::from_byte_str(path)),
         );
 
         headers.extend(HeadersAsBytesIter {