Merge pull request #1583 from williamfgc/rtd_conda

Conda environment in rtd

docs/environment.yml

+name: adios2-python-docs
+
+channels:
+  - conda-forge
+  - williamfgc
+
+dependencies:
+  - python
+  - adios2-openmpi

readthedocs.yml

 # .readthedocs.yml
-version: 1
+version: 2
 
-requirements_file: docs/requirements.txt
+conda: 
+  environment: docs/environment.yml
 
 python:
-   version: 3.7
-   use_system_site_packages: true
+  version: 3.7
+  install:
+    - requirements: docs/requirements.txt
+    - method: pip