fix phpstan for php7.1

.travis.yml

@@ -2,7 +2,7 @@ language: php
 
 php:
   - 5.6
-  - 7.0
+  - 7.1
 
 before_script:
   - composer self-update
@@ -11,15 +11,16 @@ before_script:
 install:
   - composer require satooshi/php-coveralls
   - |
-    composer global require phpstan/phpstan dev-master --prefer-dist \
-    && composer global show | grep phpstan
-
+    if [ $(phpenv version-name) = "7.1" ]; then
+    composer require --dev phpstan/phpstan;
+    fi
 script:
   - mkdir -p build/logs
-  - phpstan analyse src --level 1 -c phpstan.neon
+  - |
+    if [ $(phpenv version-name) = "7.1" ]; then
+    vendor/bin/phpstan analyse src --level 1 -c phpstan.neon;
+    fi
   - vendor/bin/phpunit --configuration phpunit.xml --coverage-clover build/logs/clover.xml
 
 after_success:
-  - travis_retry php vendor/bin/coveralls -v
-
-
+  - travis_retry php vendor/bin/coveralls -v