Fix 304 responses Cache-control override

Fix #230

.travis.yml

@@ -32,7 +32,7 @@ before_script:
       nginx
 
 script:
-  - ./test/bin/k6 run test/lib/index.js -e TESTS=basic-file-access:cache-busting:custom-errors:forbidden-files:precompressed-files-gzip:rewrites:ssl
+  - ./test/bin/k6 run test/lib/index.js -e TESTS=basic-file-access:caching:cache-busting:custom-errors:forbidden-files:precompressed-files-gzip:rewrites:ssl
 
 after_success: ./test/bin/k6 run test/lib/benchmark.js
 

h5bp/web_performance/cache_expiration.conf

@@ -15,6 +15,9 @@
 map $sent_http_content_type $expires {
   default                                 1M;
 
+  # No content
+  ""                                      off;
+
   # CSS
   ~*text/css                              1y;