ci: Build a wheel for taiga-back too

Now that the project has a `setup.py` script, we can build and publish a
wheel for it, making deployment a lot simpler.

ci/build.sh

@@ -3,6 +3,6 @@ python3.6 -m venv .venv
 
 rm -rf dist
 .venv/bin/pip install --upgrade pip setuptools wheel
-.venv/bin/pip wheel -w dist -r requirements.txt
+.venv/bin/pip wheel -w dist -r requirements.txt .
 
 sed -i '/^-i/d' requirements.txt