Add documentation on installing via conda

• Add to the documentation how to install from conda forge: https://anaconda.org/conda-forge/bilby_pipe

• Add to the README a link to the conda forge version

changed milestone to %0.2.1

created merge request !129 (merged) to address this issue

mentioned in merge request !129 (merged)

marked the checklist item Add to the documentation how to install from conda forge: https://anaconda.org/conda-forge/bilby_pipe as completed

marked the checklist item Add to the README a link to the conda forge version as completed

closed via merge request !129 (merged)

mentioned in commit 1aef358f