Add basic manpages for ctr, containerd, containerd-config

Adds initial manpages for ctr, containerd, and containerd config
commands, as well as the config.toml configuration file.

Adds targets to Makefile for generating and installing manpages.

Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com>

script/setup/install-dev-tools

@@ -8,4 +8,4 @@ go get -u github.com/stevvooe/protobuild
 go get -u github.com/alecthomas/gometalinter
 gometalinter --install >/dev/null
 go get -u github.com/LK4D4/vndr
-go get -u github.com/estesp/go-md2man
+go get -u github.com/cpuguy83/go-md2man