build: environment with holoviews

environment.yml

 name: "base"
 channels:
+  - pyviz
   - defaults
-# dependencies:
-# - add packages here
-# - one per line
-prefix: "/opt/conda"
+  - conda-forge
+dependencies:
+  - bokeh=2.0.0=py37_0
+  - holoviews=1.13.0=py_0
+  - panel=0.9.3=py_0