add cftime explicitly

.travis.yml

@@ -45,7 +45,7 @@ install:
 - conda update -q conda
 - conda config --append channels conda-forge
 
-- deps='pip numpy scipy matplotlib basemap shapely nose netcdf4 coverage coveralls pycurl pyproj seaborn simplejson sqlite statsmodels libgdal gdal'
+- deps='pip numpy scipy matplotlib basemap shapely nose netcdf4 cftime coverage coveralls pycurl pyproj seaborn simplejson sqlite statsmodels libgdal gdal'
 - conda create -q -n tcrm-env --yes $deps "python=$TRAVIS_PYTHON_VERSION"
 - source activate tcrm-env