Update README.rst with supported alternatives for simp_le#122

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meeuw wants to merge 2 commits intokuba:masterfrom

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