Created shortcode creation rest endpoint

composer.json

@@ -11,7 +11,7 @@
         }
     ],
     "require": {
-        "php": "^5.5 || ^7.0",
+        "php": "^5.6 || ^7.0",
         "zendframework/zend-expressive": "^1.0",
         "zendframework/zend-expressive-helpers": "^2.0",
         "zendframework/zend-expressive-fastroute": "^1.1",
@@ -24,7 +24,7 @@
         "symfony/console": "^3.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^4.8",
+        "phpunit/phpunit": "^5.0",
         "squizlabs/php_codesniffer": "^2.3",
         "roave/security-advisories": "dev-master",
         "filp/whoops": "^2.0",