microeco v0.2.0

Modify the help documents style, now each class has one integral documentation.
Add the fungi guild analysis from the FUNGuild database.
Fix the bug of the error from the strong collinearity in linear discriminant analysis in Lefse of trans_diff class, when sample number is small in groups.
Fix the bug of show_taxa parameter of trans_rda in trans_env class.
Add another taxa roles plot in plot_taxa_roles function of trans_network class.
Change several function names in trans_func class.
Add eigengenes analysis of modules in trans_network class.