message: feat(http): add Default trait to Body
  server::Request has a mandatory Body and client::Request has an optional Body.
  Having a default for Body makes it easier to merge the two.
diff: @@ -34,6 +34,12 @@ impl Default for Body {
  }
  }
  +impl Default for Body {
  + fn default() -> Body {
  + Body::empty()
  + }
  +}
  +
  impl Stream for Body {
  type Item = Chunk;
  type Error = ::Error;
  @@ -107,6 +113,12 @@ impl From<&'static str> for Body {
  }
  }
  +impl From<Option<Body>> for Body {
  + fn from (body: Option<Body>) -> Body {
  + body.unwrap_or_default()
  + }
  +}
  +
  fn _assert_send_sync() {
  fn _assert_send<T: Send>() {}
  fn _assert_sync<T: Sync>() {}
  