add xlwt to dependencies

docs/install-anaconda.md

@@ -9,7 +9,7 @@ conda update --all
 conda create -n wetb_py3 python=3.5
 source activate wetb_py3
 conda install setuptools_scm future h5py pytables pytest nose sphinx
-conda install scipy pandas matplotlib cython xlrd coverage
+conda install scipy pandas matplotlib cython xlrd coverage xlwt
 pip install pyscaffold pytest-cov
 ```
 

requirements.txt

@@ -5,6 +5,7 @@ scipy>=0.9
 matplotlib
 pytest
 xlrd
+xlwt
 h5py
 pandas
 tables