Allow failures for 5.2 on Travis until we figure it out

They've removed 5.2 support ...
diff --git a/.travis.yml b/.travis.yml
index 3a823f7..4f56044 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -29,6 +29,7 @@
 
 matrix:
   allow_failures:
+    - php: 5.2
     - php: hhvm
   exclude:
     - php: hhvm