add BaseURL option to namecheap creds to allow setting sandbox endpoint (#97)

docs/_providers/namecheap.md

@@ -22,6 +22,22 @@ username and key:
 }
 {% endhighlight %}
 
+You can optionally specify BaseURL to use a different endpoint - typically the
+sandbox:
+
+{% highlight json %}
+{
+  "namecheap.com":{
+    "apikey": "yourApiKeyFromNameCheap",
+    "apiuser": "yourUsername"
+    "BaseURL": "https://api.sandbox.namecheap.com/xml.response"
+  }
+}
+{% endhighlight %}
+
+if BaseURL is omitted, the production namecheap url is used.
+
+
 ## Metadata
 
 This provider does not recognize any special metadata fields unique to

providers/namecheap/namecheap.go

@@ -27,6 +27,13 @@ func newReg(m map[string]string) (providers.Registrar, error) {
 		return nil, fmt.Errorf("Namecheap apikey and apiuser must be provided.")
 	}
 	api.client = nc.NewClient(api.ApiUser, api.ApiKey, api.ApiUser)
+
+	// if BaseURL is specified in creds, use that url
+	BaseURL, ok := m["BaseURL"]
+	if ok {
+		api.client.BaseURL = BaseURL
+	}
+
 	return api, nil
 }