Rename blueprint variable from "mod" to "bp"

As I understand it, "mod" is a leftover from when blueprints were called
modules.
Rename venv/ to env/ in gitignore
Support Red Hat-style timezone config

Red Hat/Fedora doesn't have /etc/timezone, but it does have
/etc/localtime symlink - the path contains the timezone name.
Move views from __init__.py to views/main.py

This is more organized, I think.
Update hostname in fabfile
Rename templates from *.j2 to *.html

Since Flask enables Jinja2 autoescaping based on file extension, use
the "safe" filter when necessary.