Just use highest and lowest supported versions for travis build matrix.

Author: Jonathan Gaillard

.travis.yml

@@ -1,13 +1,10 @@
 language: php
 php:
   - 5.6
-  - 5.5
   - 5.4
 env:
   - EXT_VERSION=1.3.7 DB_PACKAGE=mongodb-10gen
   - EXT_VERSION=1.3.7 DB_PACKAGE=mongodb-org
-  - EXT_VERSION=1.4.5 DB_PACKAGE=mongodb-10gen
-  - EXT_VERSION=1.4.5 DB_PACKAGE=mongodb-org
   - EXT_VERSION=1.5.4 DB_PACKAGE=mongodb-10gen
   - EXT_VERSION=1.5.4 DB_PACKAGE=mongodb-org
 before_install: