Note usable methods in examples
Note usable methods in examples

This change also rewrites all example lead-ins to come *before* the examples, and not after.
chrislusf/seaweedfs,hxiaodon/seaweedfs,chrislusf/seaweedfs,k85169336/seaweedfs,chrislusf/seaweedfs,chrislusf/seaweedfs,hxiaodon/seaweedfs,k85169336/seaweedfs