Disable builds for 5.4 and 5.5

Not anymore supported in Nc and oC master.

.travis.yml

@@ -1,10 +1,7 @@
 language: php
 
 php:
-  - 5.4
-  - 5.5
   - 5.6
-#  - hhvm
   - 7
 
 env:
@@ -38,12 +35,8 @@ script:
   
 matrix:
   include:
-    - php: 5.4
+    - php: 5.6
       env: DB=mysql
-    - php: 5.4
+    - php: 5.6
       env: DB=pgsql
-#    - php: 5.4
-#      env: DB=oracle
-#  allow_failures:
-#    - php: hhvm
   fast_finish: true