Preserve HTTP method when following redirect (#1758)

Resolves #1158

This modifies http.js to uppercase the HTTP method, similar to xhr.js, before passing the request off to the transport. This causes follow-redirects to preserve the HTTP method when automatically making a request to the next URL.

lib/adapters/http.js

@@ -83,7 +83,7 @@ module.exports = function httpAdapter(config) {
 
     var options = {
       path: buildURL(parsed.path, config.params, config.paramsSerializer).replace(/^\?/, ''),
-      method: config.method,
+      method: config.method.toUpperCase(),
       headers: headers,
       agent: agent,
       auth: auth