Redeclared corneltek/cachekit as a development dependency

Although corneltek/cachekit is used in tests, PEARX itself doesn't depend on it. The unnecessary dependency not only increases the size of of the package but also imposes unnecessary version constraints on the common libraries like `symfony/*`.

Author: morozov

composer.json

@@ -2,12 +2,17 @@
     "name": "corneltek/pearx",
     "homepage": "http://github.com/phpbrew/PEARX",
     "description": "PEAR channel client",
+    "config": {
+        "platform": {
+            "php": "5.3.9"
+        }
+    },
     "require": {
         "php": ">=5.3.0",
-        "corneltek/cachekit": "^1",
         "corneltek/curlkit": "^1.0.11"
     },
     "require-dev": {
+        "corneltek/cachekit": "^1",
         "corneltek/phpunit-testmore": "dev-master",
         "phpunit/phpunit": "^4.8||^5.7"
     },