Added basic pip install jobs to CI
This merge adds some more CI testing jobs that run
- python -m pip install .
- python -c "import bilby"
- python -c "import bilby.core"
- python -c "import bilby.gw"
- python -c "import bilby.hyper"
- python -c "import cli_bilby"
to test that the basic package configuration is ok (mainly that dependencies are well defined).
This exposes an issue introduced with 0.3.6 that astropy is explicitly required.