Use poetry in build-test CI workflow

Author: bradymholt

.github/workflows/build-test.yml

@@ -15,9 +15,8 @@ jobs:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip
-          pip install -r requirements.txt
-          pip install -r test-requirements.txt
+          pip install poetry
+          poetry install          
       - name: Test with pytest
         run: |
-          pytest --cov=ynab
+          poetry run pytest --cov=ynab