Fix for PHP 7.1 behavior when calling variable functions

Fixes these notices and subsequent failure when initializing `new Task()`

PHP Notice:  Array to string conversion in /srv/www/inc/libraries/vendor/loopline-systems/closeio-api-wrapper/src/LooplineSystems/CloseIoApiWrapper/Library/ObjectHydrateHelperTrait.php on line 45

PHP Notice:  Undefined property: LooplineSystems\CloseIoApiWrapper\Model\Task::$Array in /srv/www/inc/libraries/vendor/loopline-systems/closeio-api-wrapper/src/LooplineSystems/CloseIoApiWrapper/Library/ObjectHydrateHelperTrait.php on line 45

src/LooplineSystems/CloseIoApiWrapper/Library/ObjectHydrateHelperTrait.php

@@ -40,7 +40,7 @@ public function hydrate(array $data, array $nestedObjects = [], array $method_ma
                 } else {
                     // check if setter method exists that doesn't match inflected filter format
                     if (in_array($setter, array_keys($method_mapper))) {
-                        $this->$method_mapper[$setter]($value);
+                        $this->{$method_mapper[$setter]}($value);
                     } else {
                         // value is not set - Entities should be extended if needed
                     }