changes combine_parameter_conditions so that the same parameter can be used twice (and adds tests for same); closes #8
cleans up some tests in parse_multiverse so that they pass in R6 version (except for one test that generates a warning that it shouldn't generate --- fixing #12 should cause that test to pass)
adds an execute flag to add_and_parse_code that can be used to ensure code is not executed when using that function in tests (see test-parse-multiverse for examples of this usage).
combine_parameter_conditionsso that the same parameter can be used twice (and adds tests for same); closes #8executeflag to add_and_parse_code that can be used to ensure code is not executed when using that function in tests (see test-parse-multiverse for examples of this usage).