0.18: `Client` is no longer `Send`, therefor incompatible with r2d2

[njaard]

   |
8  |   type Connection = postgres::Client;
   |                     ^^^^^^^^^^^^^^^^ `(dyn std::ops::Fn(postgres::error::DbError) + 'static)` cannot be sent between threads safely
   | 
  ::: /home/charles/.cargo/registry/src/github.com-1ecc6299db9ec823/r2d2-0.8.9/src/lib.rs:72:22
   |
72 |     type Connection: Send + 'static;
   |                      ---- required by this bound in `r2d2::ManageConnection`
   |
   = help: the trait `std::marker::Send` is not implemented for `(dyn std::ops::Fn(postgres::error::DbError) + 'static)`
   = note: required because of the requirements on the impl of `std::marker::Send` for `std::sync::Arc<(dyn std::ops::Fn(postgres::error::DbError) + 'static)>`
   = note: required because it appears within the type `postgres::connection::Connection`
   = note: required because it appears within the type `postgres::Client`

[sfackler]

Oops! Fixed in 0.18.1.