Add SoftLayer DNS provider (#59)

Add SoftLayer DNS as a DomainServiceProvider.

The SoftLayer API is a bit of a mess and treats MX and SRV records
differently. This leads to some replication and custom handling issues
to work around.

In this patch I have to change the SRV test case to be _tcp instead of
_protocol because softlayer requires a "known" protocol which AFAICT is
tcp, udp or tls. I think this will be acceptable in most cases.

Signed-off-by: Jamie Lennox <jamielennox@gmail.com>

vendor/github.com/renier/xmlrpc/test_server.rb

@@ -0,0 +1,25 @@
+# encoding: utf-8
+
+require "xmlrpc/server"
+
+class Service
+  def time
+    Time.now
+  end
+
+  def upcase(s)
+    s.upcase
+  end
+
+  def sum(x, y)
+    x + y
+  end
+
+	def error
+		raise XMLRPC::FaultException.new(500, "Server error")
+	end
+end
+
+server = XMLRPC::Server.new 5001, 'localhost'
+server.add_handler "service", Service.new
+server.serve