Add support to run Jupyter-PHP as a library

Author: Andrés Correa Casablanca

src/kernel.php

@@ -12,8 +12,21 @@
 
 namespace Litipk\JupyterPHP;
 
+define(
+    'PATH_TO_VENDOR_AS_LIBRARY',
+    __DIR__ . DIRECTORY_SEPARATOR . '..' . DIRECTORY_SEPARATOR . '..' . DIRECTORY_SEPARATOR . '..'
+);
 
-require (__DIR__.DIRECTORY_SEPARATOR.'..'.DIRECTORY_SEPARATOR.'vendor'.DIRECTORY_SEPARATOR.'autoload.php');
+define(
+    'PATH_TO_VENDOR_AS_PROJECT',
+    __DIR__ . DIRECTORY_SEPARATOR . '..' . DIRECTORY_SEPARATOR . 'vendor'
+);
+
+$pathToVendor = file_exists(PATH_TO_VENDOR_AS_LIBRARY)
+    ? PATH_TO_VENDOR_AS_LIBRARY
+    : PATH_TO_VENDOR_AS_PROJECT;
+
+require ($pathToVendor . DIRECTORY_SEPARATOR . 'autoload.php');
 
 
 use Litipk\JupyterPHP\System\System;