Change directories back after sphinx is done.

Author: tannewt

.travis.yml

@@ -29,4 +29,4 @@ script:
   - pylint adafruit_mpl3115a2.py
   - ([[ ! -d "examples" ]] || pylint --disable=missing-docstring,invalid-name,bad-whitespace examples/*.py)
   - circuitpython-build-bundles --filename_prefix adafruit-circuitpython-mpl3115a2 --library_location .
-  - cd docs && sphinx-build -E -W -b html . _build/html
+  - cd docs && sphinx-build -E -W -b html . _build/html && cd ..