Use COPY instead of ADD

[refs #42a921124d66]

Author: jfahrer

nginx/Dockerfile

@@ -5,7 +5,7 @@ RUN apt-get install -y nginx
 RUN rm /var/log/nginx/access.log && ln -s /dev/stdout /var/log/nginx/access.log
 RUN rm /var/log/nginx/error.log && ln -s /dev/stderr /var/log/nginx/error.log
 
-ADD ./html.tar.gz /var/www/
+COPY ./html/ /var/www/html/
 ADD http://example.com/index.html /var/www/html/example.html
 
 CMD ["/usr/sbin/nginx", "-g", "daemon off;"]