Merge branch 'cosmo_io' into 'master'

examples/EAGLE_100/eagle_100.yml

examples/EAGLE_100/run.sh

examples/EAGLE_12/eagle_12.yml

examples/EAGLE_12/run.sh

examples/EAGLE_25/eagle_25.yml

examples/EAGLE_25/run.sh

examples/EAGLE_50/eagle_50.yml

examples/EAGLE_50/run.sh

examples/EAGLE_6/eagle_6.yml

examples/EAGLE_6/run.sh

examples/EvrardCollapse_3D/evrard.yml

examples/SedovBlast_3D/sedov.yml

examples/main.c

examples/parameter_example.yml

src/cell.c

src/cell.h

src/common_io.c

src/cosmology.c

src/cosmology.h

src/engine.c