Add Support for Range Facets

[schlechtweg]

Adding support for Range Facet handling (Solr 3.1+).

See "http://wiki.apache.org/solr/SimpleFacetParameters?highlight=%28%28SimpleFacetParameters%29%29#Facet_by_Range" for detail parameters.

[lbdremy]

Sure go head @schlechtweg, I will merge this :). You could add the method facetByRange(field,options) and internally this method calls facet(options). The facet(options) will now accept the options.range argument which is an object containing all the parameters for faceting by range. That's just a suggestion for the api, feel free to bring your zest, but be as close as possible with the solr api (naming...) :).