Make all examples have a sensible shebang

examples/injection_examples/basic_tutorial.py

examples/injection_examples/binary_neutron_star_example.py

examples/injection_examples/calibration_example.py

examples/injection_examples/create_your_own_source_model.py

...tion_examples/create_your_own_time_domain_source_model.py

examples/injection_examples/eccentric_inspiral.py

examples/injection_examples/how_to_specify_the_prior.py

examples/injection_examples/marginalized_likelihood.py

examples/injection_examples/plot_time_domain_data.py

examples/injection_examples/sine_gaussian_example.py

examples/injection_examples/using_gwin.py

examples/open_data_examples/GW150914.py

examples/open_data_examples/GW150914_minimal.py

examples/other_examples/add_multiple_results.py

examples/other_examples/gaussian_example.py

examples/other_examples/get_LOSC_event_data.py

examples/other_examples/linear_regression_pymc3.py

...her_examples/linear_regression_pymc3_custom_likelihood.py

examples/other_examples/occam_factor_example.py