Replace buffer.buffer with more compatible version

Unforunately some browsers use a version of Buffer
that isn't based on a Uint8Array. Add logic to convert
when necessary but not make copies when unnecessary.

Author: jhiesey

lib/request.js

@@ -96,7 +96,15 @@ ClientRequest.prototype._onFinish = function () {
 	if (opts.method === 'POST' || opts.method === 'PUT' || opts.method === 'PATCH') {
 		if (capability.blobConstructor) {
 			body = new global.Blob(self._body.map(function (buffer) {
-				return buffer.buffer
+				if (buffer instanceof Uint8Array) {
+					return buffer
+				} else {
+					var buf = new Uint8Array(buffer.length)
+					for (var i = 0, len = buf.length; i < len; i++) {
+						buf[i] = buffer[i]
+					}
+					return buf
+				}
 			}), {
 				type: (headersObj['content-type'] || {}).value || ''
 			})