update example to more modern os and gcc
update example to more modern os and gcc

Summary:
Openr is only doing travis ci for ubuntu 16.04 with gcc 5 so having
the example with the older flavors can be misleading for our community.

Reviewed By: saifhhasan

Differential Revision: D7345130

fbshipit-source-id: 684cc8e58a650050b6f63c2ec20aac1857476da7

facebook/folly,facebook/folly,facebook/folly,rklabs/folly,rklabs/folly,rklabs/folly,rklabs/folly,rklabs/folly,facebook/folly,facebook/folly