Use 5.3.latest on Travis to fix the build errors

5.3.3 doesn't have ext/openssl ...

Also, allow failures on 5.3
diff --git a/.travis.yml b/.travis.yml
index 5a7eb11..e531f8d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,7 +2,7 @@
 
 php:
   - 5.2
-  - 5.3.3
+  - 5.3
   - 5.4
   - 5.5
   - 5.6
@@ -31,6 +31,7 @@
 matrix:
   allow_failures:
     - php: 5.2
+    - php: 5.3
     - php: hhvm
   exclude:
     - php: hhvm