Updates package description and dependencies

- Simplified description to match repository.
- Use PHPUnit 7 series.

Author: weierophinney

composer.json

@@ -1,6 +1,6 @@
 {
     "name": "zendframework/zend-config-aggregator-modulemanager",
-    "description": "zendframework/zend-modulemanager adapter for zendframework/zend-config-aggregator to provide zendframework/zend-mvc Module configuration which do not provide a ConfigProvider",
+    "description": "Consume zend-mvc modules as configuration providers within zend-config-aggregator.",
     "license": "BSD-3-Clause",
     "authors": [
         {
@@ -14,7 +14,7 @@
         "zendframework/zend-modulemanager": "^2.8"
     },
     "require-dev": {
-        "phpunit/phpunit": "5.7.21 || 6.3",
+        "phpunit/phpunit": "^7.0.3",
         "zendframework/zend-coding-standard": "~1.0.0",
         "zendframework/zend-config": "^3.1",
         "zendframework/zend-servicemanager": "^3.3"