allow an options hash to be passed to BlacklightMaps::GeojsonExport.new

[ebenenglish]

This PR aims to make local customizations a little bit easier by allowing an open hash to be passed as an argument to BlacklightMaps::GeojsonExport#new and BlacklightMapsHelperBehavior#serialize_geojson.

It allows something like this, for example:

render :partial => 'catalog/my_custom_map',
       :locals => {:geojson_features => serialize_geojson(map_facet_values, 
                                                          {partial: 'my_custom_popup_partial'})}

Where 'my_custom_popup_partial' is a partial that I want to display instead of the default partials included with the blacklight-maps gem.

Locally, I then only need to override BlacklightMaps::GeojsonExport#render_leaflet_popup_content (in this case, to look for the presence of the 'partial' key in the options hash) to get the functionality I want.

There might be other ways of going about accomplishing this (easier customization). Feedback/discussion welcome...

[ebenenglish]

Thanks for the merge. That's all I've got for the moment if you want to bump the version to 0.3.2.

[cbeer]

Should we spin this project out to e.g projectblacklight and give more people (e.g. @ebenenglish) the ability to release the gem?

[mejackreed]

@cbeer 👍 for that. Any process within BL we need to go through?

[cbeer]

It is done.

[cbeer]

@ebenenglish what's your rubygems.org email?

[ebenenglish]

@cbeer my rubygems.org username is the same as Github (ebenenglish). Let me know if you need the actual email address and I'll send it to you in a private email.