docs don't mention modifying the conf file

[jhellerstein]

I tried to blindly follow the installation instructions at http://pgsimilarity.projects.postgresql.org/ and met up with two frustrations:

• a handful of errors from the install scripts
• failure of the show and set examples in the install

Solution was to copy pg_similarity.conf.sample to the PGDATA directory as pg_similarity.conf and add a line to postgresql.conf:

include 'pg_similarity.conf'

Then reinstalled and all was well. Not sure if the solution is to extend the Makefile or/and fix the docs.

[eulerto]

I forgot to add that into documentation. :( Added to docs. Thanks.