Content-Length for GET requests with an empty body

Is zero. Even though the HTTP spec doesn't forbid sending a body in a
GET request, it's generally not reccomended to send a body via GET. Some
servers behave oddly with a Content-Length of 0 on a GET request since
it seems there are realted security vulnerabilities (IIS, I believe).

lib/excon/connection.rb

@@ -175,7 +175,7 @@ def request_kernel(params, &block)
           request << HTTP_1_1
 
           # calculate content length and set to handle non-ascii
-          unless params[:headers].has_key?('Content-Length')
+          unless params[:headers].has_key?('Content-Length') || (params[:method].to_s.upcase == "GET" && params[:body].to_s.empty?)
             params[:headers]['Content-Length'] = case params[:body]
             when File
               params[:body].binmode