TST: Alter test environment

Use conda to install sphinx and pytest

Author: bashtage

.travis.yml

@@ -52,10 +52,10 @@ before_install:
   - conda create -n linearmodels-test python=${PYTHON} numpy=${NUMPY} scipy=${SCIPY} pandas=${PANDAS} statsmodels matplotlib seaborn
   - source activate linearmodels-test
   - if [[ ${XARRAY} = true ]]; then conda install xarray; fi
-  - conda install --yes --quiet sphinx ipython jupyter nbconvert nbformat
-  - pip install pytest pytest-xdist coverage pytest-cov codecov sphinx doctr nbsphinx guzzle_sphinx_theme -q
-  - pip install --upgrade --no-deps sphinx
-  - pip install sphinx
+  - conda install --yes --quiet sphinx ipython jupyter nbconvert nbformat pytest pytest-xdist coverage pytest-cov
+  - pip install codecov doctr nbsphinx guzzle_sphinx_theme -q
+  # - pip install --upgrade --no-deps sphinx
+  # - pip install sphinx
   - export PYTHONHASHSEED=0
   - export MKL_NUM_THREADS=1