chore(ci): pyarrow nigtly on travis and appveyor

.travis.yml

@@ -36,7 +36,7 @@ before_install:
   - conda update -q conda
   - conda info -a
   # future: kapteyn should only be needed for astro package testing
-  - conda create -q -n test-environment -c conda-forge python=$PYTHON_VERSION setuptools==42.0.2 certifi=2019.6.16 pip numpy scipy xarray pyqt matplotlib pyopengl h5py astropy tornado cython pandas pytest pytest-asyncio numba graphviz python-graphviz pcre catboost libcxx=9.0.0 notebook scikit-learn lightgbm py-xgboost # $OPTIONAL_PACKAGES
+  - conda create -q -n test-environment -c arrow-nightlies -c conda-forge python=$PYTHON_VERSION setuptools==42.0.2 certifi=2019.6.16 pip numpy pyarrow scipy xarray pyqt matplotlib pyopengl h5py astropy tornado cython pandas pytest pytest-asyncio numba graphviz python-graphviz pcre catboost libcxx=9.0.0 notebook scikit-learn lightgbm py-xgboost # $OPTIONAL_PACKAGES
   - which pip
   - source activate test-environment
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then

appveyor.yml

@@ -18,7 +18,7 @@ install:
   - conda config --set always_yes yes --set changeps1 no
   - conda update -q conda
   - conda info -a
-  - "conda create -q -n test-environment -c conda-forge python=%PYTHON_VERSION% numpy scipy xarray pyqt matplotlib pyopengl h5py astropy tornado cython pandas cython pytest pytest-asyncio numba graphviz python-graphviz pcre lightgbm py-xgboost catboost scikit-learn ipydatawidgets ipyvolume bqplot ipympl geopandas"
+  - "conda create -q -n test-environment -c arrow-nightlies -c conda-forge python=%PYTHON_VERSION% numpy pyarrow scipy xarray pyqt matplotlib pyopengl h5py astropy tornado cython pandas cython pytest pytest-asyncio numba graphviz python-graphviz pcre lightgbm py-xgboost catboost scikit-learn ipydatawidgets ipyvolume bqplot ipympl geopandas"
   - activate test-environment
   - pip install -r requirements-ml.txt
   - pushd packages\vaex-core   && pip install . && popd