Implement --title
Created by: areeda
Fixes #975
NB: my upstream repo
(gwpy) areeda@george:gwpy[565]$git remote -v
origin https://github.com/areeda/gwpy.git (fetch)
origin https://github.com/areeda/gwpy.git (push)
upstream https://github.com/gwpy/gwpy.git (fetch)
upstream https://github.com/gwpy/gwpy.git (push)
(gwpy) areeda@george:gwpy[566]$git diff --name-only upstream/develop
gwpy/cli/cliproduct.py