Support Deployment to Heroku (#280)

* Added heroku.yml

* Added app.json

* PORT as env var

app.json

@@ -0,0 +1,42 @@
+{
+  "name": "Libreddit",
+  "description": "Private front-end for Reddit",
+  "buildpacks": [
+    {
+      "url": "https://github.com/emk/heroku-buildpack-rust"
+    },
+    {
+      "url": "emk/rust"
+    }
+  ],
+  "stack": "container",
+  "env": {
+    "LIBREDDIT_DEFAULT_THEME": {
+      "required": false
+    },
+    "LIBREDDIT_DEFAULT_FRONT_PAGE": {
+      "required": false
+    },
+    "LIBREDDIT_DEFAULT_LAYOUT": {
+      "required": false
+    },
+    "LIBREDDIT_DEFAULT_WIDE": {
+      "required": false
+    },
+    "LIBREDDIT_DEFAULT_COMMENT_SORT": {
+      "required": false
+    },
+    "LIBREDDIT_DEFAULT_POST_SORT": {
+      "required": false
+    },
+    "LIBREDDIT_DEFAULT_SHOW_NSFW": {
+      "required": false
+    },
+    "LIBREDDIT_USE_HLS": {
+      "required": false
+    },
+    "LIBREDDIT_HIDE_HLS_NOTIFICATION": {
+      "required": false
+    }
+  }
+}

heroku.yml

@@ -0,0 +1,3 @@
+build:
+  docker:
+    web: Dockerfile

src/main.rs

@@ -133,10 +133,11 @@ async fn main() {
 		.get_matches();
 
 	let address = matches.value_of("address").unwrap_or("0.0.0.0");
-	let port = matches.value_of("port").unwrap_or("8080");
+	let port = std::env::var("PORT")
+        .unwrap_or_else(|_| matches.value_of("port").unwrap_or("8080").to_string());
 	let hsts = matches.value_of("hsts");
 
-	let listener = [address, ":", port].concat();
+	let listener = [address, ":", &port].concat();
 
 	println!("Starting Libreddit...");