readme update

Author: David Frank

README.md

@@ -1,2 +1,5 @@
 # fetch-blob
+
 A Blob implementation on node.js, originally from node-fetch
+
+See [MDN doc](https://developer.mozilla.org/en-US/docs/Web/API/Blob) and [Tests](https://github.com/bitinn/fetch-blob/blob/master/test.js) for details