Merge branch 'show_code' into 'master'

pystencils/__init__.py

pystencils/display_utils.py

pystencils/kernel_wrapper.py

pystencils/test_type_interference.py

pystencils_tests/test_address_of.py

pystencils_tests/test_complex_numbers.py

pystencils_tests/test_conditional_field_access.py

pystencils_tests/test_cuda_known_functions.py

pystencils_tests/test_custom_backends.py

pystencils_tests/test_fast_approximation.py

pystencils_tests/test_interpolation.py

pystencils_tests/test_jacobi_cbackend.py

pystencils_tests/test_jacobi_llvm.py

pystencils_tests/test_opencl.py

pystencils_tests/test_source_code_comment.py

pystencils_tests/test_sum_prod.py

pystencils_tests/test_sympy_optimizations.py