Add tidiers for vegan objects

[colinbrislawn]

Feature

Add tidiers for objects from the vegan package for community ecology. This reopens old issue #23

Example usage:

adonis(dist.jaccard ~ group, data = df.samples.groups) %>% tidy()

Current workaround to get a data.frame from an vegan::adonis() output.

(adonis(dist.jaccard ~ group, data = df.samples.groups))$aov.tab %>% data.frame()

I can put together a real example using reprex to help this get started. Feel free to close this and reopen #23 if that's best