telegram: Use POST requests by default

Feature:

  To be more RFC compliant, particularly when sending
  files, we are going to default to using POST requests.
  We have been using GET requests (even when uploading files).

  PS: This causes major problems with PWRTelegram API

src/telegram.js

@@ -143,6 +143,7 @@ class TelegramBot extends EventEmitter {
       this._fixReplyMarkup(options.qs);
     }
 
+    options.method = "POST";
     options.url = this._buildURL(_path);
     options.simple = false;
     options.resolveWithFullResponse = true;