Updates mockery version. Explicitly adds phpunit dependency.

Author: Harrisonbro

composer.json

@@ -15,7 +15,8 @@
         "illuminate/session": "^5.4"
     },
     "require-dev": {
-        "mockery/mockery": "0.7.*"
+        "mockery/mockery": "~0.9",
+        "phpunit/phpunit": "~5.7"
     },
     "autoload": {
         "psr-0": {