Merge branch 'new_implementation' into 'master'

.gitlab-ci.yml

docs/RST/examples.rst

docs/RST/examples/cooling.rst

docs/RST/examples/stellar.rst

docs/RST/libstellar.rst

docs/RST/pyswiftsim.rst

docs/index.rst

examples/cooling_box/cooling.yml

examples/cooling_box/plot_cooling.py

examples/cooling_rate/cooling.yml

examples/cooling_rate/plot_cooling.py

examples/cooling_rate/run.sh

examples/initial_mass_function/plot_initial_mass_function.py

examples/initial_mass_function/run.sh

examples/lifetime/plot_lifetime.py

examples/lifetime/run.sh

pyswiftsim/__init__.py

scripts/pyswift_cooling_rate

scripts/pyswift_initial_mass_function

scripts/pyswift_lifetime