message: Update readme url
diff: # Generate User Guide in html with Sphinx
  -This user guide is hosted in readthedocs: https://adios2-adaptable-io-system-version-2.readthedocs.io/en/latest/
  +This user guide is hosted in readthedocs: https://adios2.readthedocs.io/en/latest/
  Python v2.7 or above is required to build the Sphinx based user guide. Sphinx can be downloaded using pip `pip install sphinx`. In addition:
  