Resolves issue #1398

This issue is incorrectly titled - the G-test error occurs here. In short, this PR removes the abilit to use group_significance.py on a table which is relative abundance.
Resolves forum users concern

Forum posts frequently cite the warning that table has no metadata as an error when using group_significance.py. It actually does not cause failures, just a warning. This clarifies the message.
Missing word.
Merge pull request #1545 from wdwvt1/group_sig_g_test

Group sig g test