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/softlayer/softlayer-go/sl/version.go

@@ -0,0 +1,47 @@
+/**
+ * Copyright 2016 IBM Corp.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/**
+ * AUTOMATICALLY GENERATED CODE - DO NOT MODIFY
+ */
+
+package sl
+
+import "fmt"
+
+type VersionInfo struct {
+	Major int
+	Minor int
+	Patch int
+	Pre   string
+}
+
+var Version = VersionInfo{
+	Major: 0,
+	Minor: 1,
+	Patch: 0,
+	Pre:   "alpha",
+}
+
+func (v VersionInfo) String() string {
+	result := fmt.Sprintf("v%d.%d.%d", v.Major, v.Minor, v.Patch)
+
+	if v.Pre != "" {
+		result += fmt.Sprintf("-%s", v.Pre)
+	}
+
+	return result
+}