leave cache-control header alone in its entirety if disable_caching = false

closes #616

Author: glaszig

lib/mini_profiler.rb

@@ -425,14 +425,14 @@ def inject_profiler(env, status, headers, body)
       # Rack::ETag has already inserted some nonesense in the chain
       content_type = headers[Rack::CONTENT_TYPE]
 
+      headers['x-miniprofiler-original-cache-control'] = headers[Rack::CACHE_CONTROL] unless headers[Rack::CACHE_CONTROL].nil?
+
       if config.disable_caching
         headers.delete(Rack::ETAG)
         headers.delete('date') || headers.delete('Date')
+        headers[Rack::CACHE_CONTROL] = "no-store, must-revalidate, private, max-age=0"
       end
 
-      headers['x-miniprofiler-original-cache-control'] = headers[Rack::CACHE_CONTROL] unless headers[Rack::CACHE_CONTROL].nil?
-      headers[Rack::CACHE_CONTROL] = "#{"no-store, " if config.disable_caching}must-revalidate, private, max-age=0"
-
       # inject header
       if headers.is_a? Hash
         headers['x-miniprofiler-ids'] = ids_comma_separated(env)