Removed php71 from testing envs

Author: vgarvardt

.travis.yml

@@ -3,10 +3,9 @@ language: php
 php:
   - '5.6'
   - '7.0'
-  - '7.1'
 
 install:
-  - composer install
+  - composer install -n
 
 script:
   - phpunit