Update godocs to include info useful for private clouds.
diff --git a/context.go b/context.go
index 21d0ae0..57f0801 100644
--- a/context.go
+++ b/context.go
@@ -87,6 +87,10 @@
// ProviderByName will locate a provider amongst those previously registered, if it exists.
// If the named provider has not been registered, an ErrProvider error will result.
+//
+// You may also specify a custom Identity API URL.
+// Any provider name that contains the characters "://", in that order, will be treated as a custom Identity API URL.
+// Custom URLs, important for private cloud deployments, overrides all provider configurations.
func (c *Context) ProviderByName(name string) (p Provider, err error) {
for provider, descriptor := range c.providerMap {
if name == provider {