aes_string()` deprecated

[Masoleno]

I keep getting the following warning when using plot_richness():

Warning message:
aes_string() was deprecated in ggplot2 3.0.0.
ℹ Please use tidy evaluation idioms with aes().
ℹ See also vignette("ggplot2-in-packages") for more information.
ℹ The deprecated feature was likely used in the phyloseq package.
Please report the issue at https://github.com/joey711/phyloseq/issues

Just thought I'd raise it in case you're not aware.

Thanks for such a great package!