Add pg as an optional dependency.

Closes #1333
- Change PostgreSQL build on Travis from an allowed failure to
  failing the tests just like sqlite3 and MySQL.
Adds SIGTERM handling

closes #4403
- adds SIGTERM handler to match SIGINT handler
Merge pull request #4404 from Haegin/add-sigterm-handler

Adds SIGTERM handling
Remove image related text from meta description.

Closes #4408
Merge pull request #4395 from jaswilli/pg

Add pg as an optional dependency.
Merge pull request #4410 from jaswilli/issue-4408

Remove image related text from meta description.
First pass of the dashboard markup