Add global Authenticate() function.
Also finishes work started in last commit.
diff --git a/package.go b/package.go
index c05681e..396e523 100644
--- a/package.go
+++ b/package.go
@@ -1 +1,7 @@
+// Gophercloud provides a multi-vendor interface to OpenStack-compatible clouds which attempts to follow
+// established Go community coding standards and social norms.
+//
+// Unless you intend on contributing code to the SDK, you will almost certainly never have to use any
+// Context structures or any of its methods. Contextual methods exist for easier unit testing only.
+// Stick with the global functions unless you know exactly what you're doing, and why.
package gophercloud