cleanup request methods, make sure to merge params[:headers]

lib/fog/aws/s3.rb

@@ -95,17 +95,7 @@ module Fog
         params[:headers]['Date'] = Time.now.utc.strftime("%a, %d %b %Y %H:%M:%S +0000")
         params[:headers]['Authorization'] = "AWS #{@aws_access_key_id}:#{signature(params)}"
 
-        response = @connection.request({
-          :block    => params[:block],
-          :body     => params[:body],
-          :expects  => params[:expects],
-          :headers  => params[:headers],
-          :host     => params[:host],
-          :method   => params[:method],
-          :parser   => params[:parser],
-          :path     => params[:path],
-          :query    => params[:query]
-        })
+        response = @connection.request(params)
 
         response
       end

lib/fog/rackspace/servers.rb

@@ -66,7 +66,7 @@ module Fog
           :expects  => params[:expects],
           :headers  => {
             'X-Auth-Token' => @auth_token
-          },
+          }.merge!(params[:headers] || {}),
           :host     => @host,
           :method   => params[:method],
           :path     => "#{@path}/#{params[:path]}"

lib/fog/slicehost.rb

@@ -51,7 +51,7 @@ module Fog
       response = @connection.request({
         :body     => params[:body],
         :expects  => params[:expects],
-        :headers  => headers,
+        :headers  => headers.merge!(params[:headers] || {}),
         :host     => @host,
         :method   => params[:method],
         :parser   => params[:parser],