update README with intro and internals

Makefile

@@ -1,6 +1,7 @@
 
 PREFIX=/usr/local
 
+.PHONY: install
 install:
 	install -Dm 644 common_sshconfig -t "$(PREFIX)/lib/diyvpn"
 	install -Dm 755 diyvpn.sh -t "$(PREFIX)/lib/diyvpn"
@@ -10,6 +11,7 @@ install:
 	install -dm 755 "$(PREFIX)/lib/systemd/user-generators"
 	ln -snf ../../diyvpn/diyvpn.sh "$(PREFIX)/lib/systemd/user-generators/diyvpn"
 
+.PHONY: uninstall
 uninstall:
 	rm -rf "$(PREFIX)/lib/diyvpn" \
 		"$(PREFIX)/bin/diyvpnctl" \