deps: Update to a more recent rocket and rust toolchain

With this patch, Plume will be use a more up-to-date revision of
Rocket, that works with nightly-2018-07-17. It may have been able to
make it work with a more recent revision, but it turns out rocket has
introduced several breaking changes so I’d rather fix those.

Besides updating rocket_i18n and rocket_csrf to use the same revision
than Plume, this patch deals with the new implementation of the
Uri<'_> type. It silents a class of warnings, to deal with a change in
rustc which affects diesel. This latter change should be reverted as
soon as diesel releases a new version of its crate.

src/routes/blogs.rs

@@ -65,7 +65,10 @@ fn new(user: User, conn: DbConn) -> Template {
 
 #[get("/blogs/new", rank = 2)]
 fn new_auth() -> Flash<Redirect>{
-    utils::requires_login("You need to be logged in order to create a new blog", uri!(new))
+    utils::requires_login(
+        "You need to be logged in order to create a new blog",
+        uri!(new).into()
+    )
 }
 
 #[derive(FromForm, Validate, Serialize)]