Fix for updateStatus function

The original function returns the error:
"Error in fromJSON(rawToChar(url.data$content)) : unexpected character
'<'"

GET function returns status_code = 400 and the content in raw HTML which
causes troubles.
I've added few prepocessing functions for message to support other
languages and change GET method to POST.
Merge pull request #4 from Amice13/master

Fix for updateStatus function