chore(tests): add git version echo to windows tests

Appveyor has conflicting information on the git version that they use. This change makes sure that
we echo out the git version during test runs, after npm install.

Author: jimthedev

appveyor.yml

@@ -14,6 +14,7 @@ test_script:
   # Output useful info for debugging.
   - node --version
   - npm --version
+  - git --version
   # run tests
   - npm test