Add more formatting options for my_activity.py
Add more formatting options for my_activity.py

Support --output-format-heading for the headings
('Issues:', etc), and a simple --markdown flag that sets
item and heading formats to something markdown friendly.

R=deymo@chromium.org, szager@chromium.org, deymo

Review URL: https://codereview.chromium.org/116873002

git-svn-id: bd64dd6fa6f3f0ed0c0666d1018379882b742947@243204 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

svn2github/chromium-depot-tools,svn2github/chromium-depot-tools,svn2github/chromium-depot-tools