SOFTLAYER: Mark provider as unmaintained (#1080)

* Warn about Softlayer

docs/_providers/softlayer.md

@@ -7,6 +7,10 @@ jsId: SOFTLAYER
 
 # SoftLayer DNS Provider
 
+NOTE: This provider is currently has no maintainer. We are looking for
+a volunteer. If this provider breaks it may be disabled or removed if
+it can not be easily fixed.
+
 ## Configuration
 To authenticate with SoftLayer requires at least a `username` and `api_key` for authentication. It can also optionally take a `timeout` and `endpoint_url` parameter however these are optional and will use standard defaults if not provided.
 
@@ -44,4 +48,4 @@ D("example.tld", REG_NONE, DnsProvider(SOFTLAYER),
 
     A("test","1.2.3.4")
 );
-{%endhighlight%}
+{%endhighlight%}