If you just want to post messages I would recommend to use an Incoming Webhook.
They are specifically designed for that purpose and easier to use than API calls.
It was added on Sep 18th: https://core.telegram.org/bots/api Usage: In the JSON of the message you will receive a file_id as before.
The maximum size of a file obtained through this method is 20MB.
Error: Obtained when a file large than 20mb is used.(Shown below) On success, a File object is returned.