Include Buffer source option

In accordance with documentation of [`image-parser`](https://github.com/IonicaBizau/image-parser#params)

Author: benwiley4000

README.md

@@ -80,7 +80,7 @@ Converts the provided image in ASCII art.
 
 #### Params
 
-- **String** `source`: The path/url to the image.
+- **String|Buffer** `source`: The path/url to the image or a `Buffer` object.
 - **Object|String** `options`: The path to the image or an object containing the following fields:
 
  **Size Options**: