Add limit to logined user only.

- limited to logined user in add workout log view.
- only show workout log list for logined user in changlist view.
- pep8 fix for admin.py
Merge pull request #19 from gary-pei/master

default to the logged-in user for both workout log add view and changelist view
Merge pull request #20 from ns-uw/master

Modified CSS, templates and views (added users_view.html) to enable site...