Add version number to the joi instance

Author: Marsup

API.md

@@ -7,6 +7,7 @@
 <!-- toc -->
 
 - [Joi](#joi)
+  - [`version`](#version)
   - [`validate(value, schema, [options], [callback])`](#validatevalue-schema-options-callback)
   - [`compile(schema)`](#compileschema)
   - [`assert(value, schema, [message])`](#assertvalue-schema-message)
@@ -134,6 +135,10 @@
 
 ## Joi
 
+### `version`
+
+Property showing the current version of joi being used.
+
 ### `validate(value, schema, [options], [callback])`
 
 Validates a value using the given schema and options where:

lib/index.js

@@ -347,6 +347,8 @@ internals.root = function () {
         }).or('setup', 'validate'))
     })).strict();
 
+    root.version = require('../package.json').version;
+
     return root;
 };