periods replace with commas in input names/ids

[charleskoehl]

For example, if a text input has the name 'address.city', and it has an error, the error object returned by require('joi-errors-for-forms').form is
{address,city: "required"} instead of {address.city: "required"}

[lukaszczerpak]

it appears to start occurring since joi@11.0.0 and is related to how path is constructed (hapijs/joi#1302).
Changing from:

var path = detail.path;

to:

var path = detail.path.join('.');

fixes the problem.