[DOC] Added README.md for generating assets

assets/README.md

+# Assets loaded in with IPFS
+
+## Generating docs
+
+Do not edit the .go files directly.
+
+Instead, edit the source files and use `go2doc` from within the
+assets directory:
+
+```
+go get github.com/whyrusleeping/doc2go
+go generate
+```