install symfony demo with installer

app/config/routes/dev/framework.yaml

@@ -0,0 +1,3 @@
+_errors:
+    resource: '@FrameworkBundle/Resources/config/routing/errors.xml'
+    prefix: /_error

app/config/routes/dev/web_profiler.yaml

@@ -0,0 +1,7 @@
+web_profiler_wdt:
+    resource: '@WebProfilerBundle/Resources/config/routing/wdt.xml'
+    prefix: /_wdt
+
+web_profiler_profiler:
+    resource: '@WebProfilerBundle/Resources/config/routing/profiler.xml'
+    prefix: /_profiler