Correct paths for doc validation

- Set PYTHONPATH so doc validation can find LensKit
- Re-run the Getting Started notebook

azure-pipelines.yml

@@ -29,7 +29,7 @@ jobs:
 
   - script: |
       conda create -n lkpy -qy $(conda.deps)
-      conda install -n lkpy -qy ipykernel nbformat jupyter
+      conda install -n lkpy -qy ipykernel nbformat jupyter matplotlib
     displayName: Create Anaconda environment
   
   - script: |
@@ -68,11 +68,6 @@ jobs:
       testResultsFiles: 'build/test-results.xml'
       testRunTitle: 'Publish test results for Python $(python.version)'
 
-  - script: |
-      source activate lkpy
-      cp -r ml-100k doc
-      python3 -m pytest --nbval-lax doc
-
   - script: |
       source activate lkpy
       env NUMBA_DISABLE_JIT=1 python3 -m pytest --cov=lenskit --cov-report=xml --cov-report=html -m 'not eval'
@@ -101,6 +96,12 @@ jobs:
       summaryFileLocation: '$(System.DefaultWorkingDirectory)/coverage.xml'
       reportDirectory: '$(System.DefaultWorkingDirectory)/htmlcov'
 
+  - script: |
+      source activate lkpy
+      cp -r ml-100k doc
+      export PYTHONPATH="$PWD"
+      python3 -m pytest --nbval-lax doc
+
 - job: 'LinuxVanilla'
   pool:
     vmImage: ubuntu-16.04