Fix version requirements in composer.json

Author: swissspidy

composer.json

@@ -19,11 +19,11 @@
     "require": {
         "php": ">=5.4",
         "wp-cli/package-command": "^2",
-        "wp-cli/wp-cli": "2"
+        "wp-cli/wp-cli": "^2"
     },
     "require-dev": {
         "wp-cli/extension-command": "^2",
-        "wp-cli/wp-cli-tests": "2"
+        "wp-cli/wp-cli-tests": "^2.0.7"
     },
     "config": {
         "platform": {