Set the --dev option for travis composer install command.
diff --git a/.travis.yml b/.travis.yml
index 070b23c..1f6a595 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -15,7 +15,7 @@
 
 before_script:
   - curl -s http://getcomposer.org/installer | php
-  - php composer.phar install
+  - php composer.phar install --dev
   - sh -c "if [ '$DB' = 'pgsql' ] || [ '$DB' = 'pdo/pgsql' ]; then psql -c 'DROP DATABASE IF EXISTS ci_test;' -U postgres; fi"
   - sh -c "if [ '$DB' = 'pgsql' ] || [ '$DB' = 'pdo/pgsql' ]; then psql -c 'create database ci_test;' -U postgres; fi"
   - sh -c "if [ '$DB' = 'mysql' ] || [ '$DB' = 'mysqli' ] || [ '$DB' = 'pdo/mysql' ]; then mysql -e 'create database IF NOT EXISTS ci_test;'; fi"