Add new providers to readme

readme.md

@@ -195,6 +195,13 @@ Each of the generator properties (like `name`, `address`, and `lorem`) are calle
     safeColorName          // 'fuchsia'
     colorName              // 'Gainsbor'
 
+### `Faker\Provider\Payment`
+
+    creditCardType         // 'MasterCard'
+    creditCardNumber($type = null) // '4485480221084675'
+    creditCardExpirationDate($valid = true) // DateTime('2014-10-23 13:46:23')
+    creditCardExpirationDateString($valid = true) // '10/14'
+
 ## Unique and Optional modifiers
 
 Faker provides two special providers, `unique()` and `optional()`, to be called before any provider. `optional()` can be useful for seeding non-required fields, like a mobile telephone number ; `unique()` is required to populate fields that cannot accept twice the same value, like primary identifiers.