with updated version of R, maybe I don't need to install older versions of dependencies

updated R to try to install ANCOMBC and lefser

trying to avoid installing numpy with apt-get
also probably cleaner to avoid recommends

also installing a few other python packages with pip to avoid pulling in numpy with apt-get

Trying to get metaphlan to work - hopefully pip installing metaphlan will pull it in?

many python2 versions of packages are no longer in ubuntu 20.04

major change: update to ubuntu 20.04 and python3

because python2 is deprecated

3.6.2 isn't on CRAN anymore

Signed-off-by: Mark McCahill <mark.mccahill@duke.edu>

to fix "dpkg-sig: not found"

Fixed conflicts between staging and master

so I could get rid of all the "DEBIAN_FRONTEND=noninteractive" prefixes to apt commands