Update README.rst with supported alternatives for simp_le#122

Open

meeuw wants to merge 2 commits intokuba:masterfrom meeuw:patch-1

+7

Commits on Jan 27, 2017

Mention in README that this is not actively maintained
ykarikos
authored

Commits on Sep 15, 2018

Mention certbot in README, link to https://github.com/meeuw/simp_le2certbot to help the migration.
meeuw
committed