Hard-code S3 bucket URL (rather than using EC2 tag)

Turns out tags aren't the right thing to use since you can't specify
them for auto-scaling group instances. Hence, we need everything to
build the server in user-data so we how hard-code the S3 URL at the top
of user data.
A "dev" Docker image can now be built

It is intended to be standalone, without environmental variables being
passed in. It contains SQlite database and logs to /tmp for now.

Building the dev image is equivalent to using the makefile to build a
local version.
Use the standard Ubuntu base image

The base Tangent image is potentially confusing as we don't have good
audit on what's in it. Plus it's more explicit to build everything in
the project base image.
Generate uWSGI stats (for uwsgitop)
Ensure tests pass without using Docker container
Improve env var handling in settings

Ensure the appropriate ones are passed in.
Add Fabric task to sync all files to S3 files
Rework start_webserver.sh script to not download stuff

The idea being the env file should be downloaded from S3 inadvance and
mounted into the container. This keeps things simpler which is a good
thing.
Use Fabric to build Docker images

As Fabric is much nicer than Bash and avoids the need to duplicate the
client/project name config.
Ignore sensitive files

It's still useful to have them locally so they can be pushed up to S3
using Fabric. But we shouldn't allow them to be committed.
Enhance user-data bootstrapping

Changes:

- Use a pretty `notify` function
- Fetch the Docker config file from S3 during the "base" bootstrap file
- Specify the region for `aws s3 cp` commands.