content: Update mjanja blog links to new host

I migrated from mjanja.co.ke to mjanja.ch (including https). There
are 301's in place to handle these, but we might as well fix these
links.

Signed-off-by: Alan Orth <alan.orth@gmail.com>
Merge pull request #80 from alanorth/mjanja-migration

content: Update mjanja blog links to new host