Improve travis settings backported from v4 settings

.travis.yml

@@ -1,5 +1,7 @@
 language: php
 
+sudo: false
+
 php:
   - 5.3
   - 5.4
@@ -9,19 +11,31 @@ php:
   - hhvm
 
 matrix:
+  include:
+    - php: 5.3
+      env: COLLECT_COVERAGE=true
+    - php: 5.4
+      env: COLLECT_COVERAGE=true
+    - php: 5.5
+      env: COLLECT_COVERAGE=true
+    - php: 5.6
+      env: COLLECT_COVERAGE=true
+    - php: 7.0
+    - php: hhvm
   allow_failures:
     - php: 7.0
   fast_finish: true
 
+cache:
+  directories:
+    - $HOME/.composer/cache
+
 install:
-  - travis_retry composer install
+  - travis_retry composer install --prefer-dist
 
 script:
   - phpunit --coverage-text --coverage-clover=coverage.clover
 
 after_script:
-- wget https://scrutinizer-ci.com/ocular.phar
-- if [ "$TRAVIS_PHP_VERSION" == "5.3" ]; then php ocular.phar code-coverage:upload --format=php-clover coverage.clover; fi
-- if [ "$TRAVIS_PHP_VERSION" == "5.4" ]; then php ocular.phar code-coverage:upload --format=php-clover coverage.clover; fi
-- if [ "$TRAVIS_PHP_VERSION" == "5.5" ]; then php ocular.phar code-coverage:upload --format=php-clover coverage.clover; fi
-- if [ "$TRAVIS_PHP_VERSION" == "5.6" ]; then php ocular.phar code-coverage:upload --format=php-clover coverage.clover; fi
+ - wget https://scrutinizer-ci.com/ocular.phar
+ - if [ "$COLLECT_COVERAGE" == "true" ]; then php ocular.phar code-coverage:upload --format=php-clover coverage.clover; fi