Fix issues with using a different/custom path for the public folder

[ghinda]

Because of the hardcoded _public/js/dontUseMe path in the plugin, the partials.js was not being created when using a different value, other than _public, for the config.path.public parameter.

For example, having set

paths: {
  public: 'public'
}

in the Brunch config.js file, the partials.js file is not created at all.

This fixes the issue by replacing the _public part of the hardcoded path, with the config.path.public parameter, from the Brunch config file.

[GulinSS]

some days later I will increment version in npm

[ghinda]

Wow, that was a fast merge! Would be great if you could post a comment here when you get to update it in npm.