Update coveralls dependency

Author: tacovandenbroek

.travis.yml

@@ -8,4 +8,4 @@ install: composer install
 script: ./vendor/bin/phpunit
 
 after_success:
-  - travis_retry php ./vendor/bin/coveralls -v
+  - travis_retry php ./vendor/bin/php-coveralls -v

composer.json

@@ -17,7 +17,7 @@
   },
   "require-dev": {
     "phpunit/phpunit": ">=5-stable",
-    "satooshi/php-coveralls": "dev-master"
+    "php-coveralls/php-coveralls": "^2"
   },
   "autoload": {
     "psr-4": {