fix: return correct not found for disconnected client and fix tests

Tests weren't passing because autopush had a dependency change for FCM.
This updates the travis test to pull down the current dependencies for
autopush for integration tests.

Closes #89

.travis.yml

@@ -11,6 +11,8 @@ dist: trusty
 
 install:
 - make ddb
+- curl https://raw.githubusercontent.com/mozilla-services/autopush-rs/master/requirements.txt > requirements.txt
+- curl https://raw.githubusercontent.com/mozilla-services/autopush-rs/master/test_requirements.txt > test_requirements.txt
 - pip install --upgrade pip
 - pip install -r requirements.txt
 - pip install -r test-requirements.txt

src/http.rs

@@ -57,7 +57,7 @@ impl Service for Push {
                             Ok(hyper::Response::new().with_status(StatusCode::Ok))
                         } else {
                             Ok(hyper::Response::new()
-                                .with_status(StatusCode::BadGateway)
+                                .with_status(StatusCode::NotFound)
                                 .with_body("Client not available."))
                         }
                     } else {