Allow ArrayBuffer and related views as data

In order to push binary data under the form of ArrayBuffer and
its related views (Int8Array, ...) one needs not to stringify
those.

For the XHR adapter there is nothing to do as it natively supports
ArrayBuffer in req.send().

Node's http adapter supports only string or Buffer thus a
transformation to Buffer is required before setting content length
header.

lib/adapters/http.js

@@ -4,6 +4,7 @@ var transformData = require('./../transformData');
 var utils = require('./../utils');
 var http = require('http');
 var url = require('url');
+var Buffer = require('buffer').Buffer;
 
 module.exports = function httpAdapter(resolve, reject, config) {
   // Transform request data
@@ -13,6 +14,10 @@ module.exports = function httpAdapter(resolve, reject, config) {
     config.transformRequest
   );
 
+  if (utils.isArrayBuffer(data)) {
+    data = new Buffer(new Uint8Array(data));
+  }
+
   // Merge headers
   var headers = utils.merge(
     defaults.headers.common,

lib/adapters/xhr.js

@@ -87,6 +87,10 @@ module.exports = function xhrAdapter(resolve, reject, config) {
     }
   }
 
+  if (utils.isArrayBuffer(data)) {
+    data = new DataView(data);
+  }
+
   // Send the request
   request.send(data);
 };