Remove the word middleware (#1067)

* 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

plugin/pprof/README.md

@@ -0,0 +1,41 @@
+# pprof
+
+*pprof* publishes runtime profiling data at endpoints under /debug/pprof.
+
+You can visit `/debug/pprof` on your site for an index of the available endpoints. By default it
+will listen on localhost:6053.
+
+> This is a debugging tool. Certain requests (such as collecting execution traces) can be slow. If
+> you use pprof on a live site, consider restricting access or enabling it only temporarily.
+
+For more information, please see [Go's pprof
+documentation](https://golang.org/pkg/net/http/pprof/) and read
+[Profiling Go Programs](https://blog.golang.org/profiling-go-programs).
+
+## Syntax
+
+~~~
+pprof [ADDRESS]
+~~~
+
+If not specified, ADDRESS defaults to localhost:6053.
+
+## Examples
+
+Enable pprof endpoints:
+
+~~~
+pprof
+~~~
+
+Listen on an alternate address:
+
+~~~
+pprof 10.9.8.7:6060
+~~~
+
+Listen on an all addresses on port 6060:
+
+~~~
+pprof :6060
+~~~