update install documentation URL

[missinglink]

The error description "For full instructions on setting up Pelias, see http://pelias.io/install.html" is dated and could do with an update.

dbclient/src/configValidation.js

Line 37 in 67f15ba

console.error('For full instructions on setting up Pelias, see http://pelias.io/install.html');

[missinglink]

I think we probably want to just link people to the docker repo since we haven't advocated installing it all from scratch for some time @orangejulius ?