Missing blank line when using POST

[bullestock]

RestClient::request() adds a blank line between headers and request body if the method is GET, but this blank line is needed for other methods too, such as POST.

[DaKaZ]

@bullestock thanks for reporting this - its crazy to think that this has been an issue for this long! I verified the format here: https://www.w3.org/Protocols/rfc2616/rfc2616-sec4.html and it clearly says there should be a CRLF between the headers and message body. I have fixed this issue.