* doc update
Go through all README and fix mistakes, extend example and let more
corefile snippets be test for validity.
* Cant use spefic addr in test
* Rename middleware to plugin
first pass; mostly used 'sed', few spots where I manually changed
text.
This still builds a coredns binary.
* fmt error
* Rename AddMiddleware to AddPlugin
* Readd AddMiddleware to remain backwards compat