Decrease the Diesel pool size to 1

R2D2 tries to immediately populate the pool, and we're running out of
connections when it does so. Since Diesel is only used on one endpoint,
we don't need 10 connections.

Author: sgrif

.buildpacks

@@ -1,5 +1,5 @@
 https://github.com/rcaught/heroku-buildpack-cmake#e4e2c9e
-https://github.com/emk/heroku-buildpack-rust#035823
+https://github.com/mmirate/heroku-buildpack-rust#f1cf6643e
 https://github.com/tonycoco/heroku-buildpack-ember-cli
 https://github.com/ryandotsmith/nginx-buildpack.git#af813ba
 https://github.com/sgrif/heroku-buildpack-diesel#43267f2

src/app.rs

@@ -54,7 +54,7 @@ impl App {
             .helper_threads(if config.env == ::Env::Production {3} else {1})
             .build();
         let diesel_db_config = r2d2::Config::builder()
-            .pool_size(if config.env == ::Env::Production {10} else {1})
+            .pool_size(if config.env == ::Env::Production {1} else {1})
             .helper_threads(if config.env == ::Env::Production {3} else {1})
             .build();