Fix Composer to 1.x and update test dependencies.

Author: Test

.travis.yml

@@ -1,9 +1,8 @@
 language: php
 php:
-  - 5.6
-  - 7.0
-  - 7.1
   - 7.2
+  - 7.3
+  - 7.4
 
 sudo: false
 
@@ -12,7 +11,7 @@ git:
 
 before_install:
   - phpenv config-rm xdebug.ini
-  - composer --verbose self-update
+  - composer --verbose self-update --1
   - composer --version
 
 install:

composer.json

@@ -19,7 +19,7 @@
         }
     },
     "require-dev": {
-        "composer/composer": "dev-master",
-        "phpunit/phpunit": "^4.4.0"
+        "composer/composer": "1.*",
+        "phpunit/phpunit": "^6"
     }
 }