Updated build matrix

We need to run tests for each PHP version against both v2.7 and v3 of
zend-servicemanager.

.travis.yml

@@ -26,18 +26,27 @@ matrix:
   include:
     - php: 5.5
       env:
-        - SERVICE_MANAGER_VERSION="^2.7.5"
         - EXECUTE_CS_CHECK=true
-    - php: 5.6
+    - php: 5.5
       env:
         - SERVICE_MANAGER_VERSION="^2.7.5"
+    - php: 5.6
+      env:
         - EXECUTE_TEST_COVERALLS=true
         - DEPLOY_DOCS="$(if [[ $TRAVIS_BRANCH == 'master' && $TRAVIS_PULL_REQUEST == 'false' ]]; then echo -n 'true' ; else echo -n 'false' ; fi)"
         - PATH="$HOME/.local/bin:$PATH"
+    - php: 5.6
+      env:
+        - SERVICE_MANAGER_VERSION="^2.7.5"
     - php: 7
+    - php: 7
+      env:
+        - SERVICE_MANAGER_VERSION="^2.7.5"
     - php: hhvm 
+    - php: hhvm
+      env:
+        - SERVICE_MANAGER_VERSION="^2.7.5"
   allow_failures:
-    - php: 7
     - php: hhvm
 
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