mecoturn v0.3.0

• fix filter_thres parameter bug in the cal_diff function of taxaturn class
• more packages in 'Imports' part

mecoturn v0.2.0

• add glmm method in cal_diff function of taxaturn class
• filter needless groups according to provided ordered_group in taxaturn class
• add group2num parameter in cal_diff function of taxaturn class
• also return res_change_pair in taxaturn class

mecoturn v0.1.0

Two classes (betaturn and taxaturn) are created to study microbial turnover.