microeco v0.19.0

• add glmm method in trans_diff and trans_alpha
• restructure lme method in cal_diff of trans_alpha
• add maaslin2 method in trans_diff and cal_cor of trans_env
• add transformation parameter in trans_diff
• add color_group_map param in plot_diff_bar of trans_diff
• add SRS method in rarefy_samples of microtable
• add coord_flip param in plot_bar of trans_abund
• add clustering_plot parameter in plot_bar of trans_abund
• allow petal_color multiple values in plot_venn of trans_venn
• add return_model parameter in cal_diff of trans_alpha
• more data checking in plot_cor of trans_env
• default character2numeric FALSE in trans_env
• add return_model parameter in cal_diff of trans_alpha
• update example dataset.RData