Travis Config Update

Author: eblount

.travis.yml

@@ -5,14 +5,9 @@ php:
   - 5.6
   - 7.0
 
-env:
-  matrix:
-    - COMPOSER_FLAGS="--prefer-lowest"
-    - COMPOSER_FLAGS=""
-
 before_script:
   - travis_retry composer self-update
-  - travis_retry composer install ${COMPOSER_FLAGS} --no-interaction --prefer-source
+  - travis_retry composer install --no-interaction --prefer-source
 
 script:
   - phpunit --coverage-text --coverage-clover=coverage.clover