Adequate links
Fix internal links in the STL algos series

I can't find a way to write the posts list only once. I have tried with
a file in _data, to be included with the appropriate {% for %}
statement, and it didn't work (it seems that my server does not render
output Liquid markup); I have also tried with an file in _include, to be
properly {% capture %}-ed and markdownified, but it does not work
either. What's wrong?
Add post on Haash tables