Change value in file v2.0.0

Fixed notfound_exit input doing the exact opposite (Step as failed wrong value logic · Issue #6 · bitrise-steplib/steps-change-value · GitHub). By default, it will now fail the step if the text that needs to be replaced cannot be found in the given file.

Thanks @BonnetM for submitting a fix (Flip inputIsFailIfOldValueNotFound logic by BonnetM · Pull Request #7 · bitrise-steplib/steps-change-value · GitHub)!