Design responsive email template

A cool feature would be for laddr to send out automatic weekly/monthly newsletters to interested members.

Based on data currently available the newsletter could include:
- New blog posts since last newsletter
- New project activity and project buzz
- New members
- New projects
- Upcoming events

With extensions to the backend the newsletter could further include:
- External events we wish to promote
- Special announcements that get queued up specifically for inclusion in the next newsletter
- Projects with open help requests
- Members with open help offers
- Sponsors / civic job listings