Move tests for tardis.util from io/tests/test_config_reader to tests/test_util.py

[wkerzendorf]

The tests are located in the wrong place.
Also add tests for 'si2' and other species without space.

There are functions in test_config_reader (like test_species_string_to_species() that test functions that are located in util. These functions should be moved to test_util.py.

[thegyro]

Thanks for the clarification! The function test_element_symbol2atomic_number is present at both test_config_reader.py as well as test_util.py. It looks like both are doing the same job (just that the former seems to check for more elements rather than just silicon and it is covering more ground/cases than the latter). I would say to remove the current test_element_symbol2atomic_number function written in test_util.py and replace it with the one in test_config_reader.

[unoebauer]

FYI @wkerzendorf: Move has been performed - no longer an issue - closing...