Fix path issue for highcharts-more & highcharts-3d as well make use of path.join
Fix path issue for highcharts-more & highcharts-3d as well make use of path.join

Rename a variable to be less potentially ES6-conflicting

gregjopa/ember-highcharts,CubiclDev/ember-highcharts,gregjopa/ember-highcharts,CubiclDev/ember-highcharts,ahmadsoe/ember-highcharts,supersabillon/ember-highcharts,gregjopa/ember-highcharts,supersabillon/ember-highcharts,ahmadsoe/ember-highcharts,supersabillon/ember-highcharts,ahmadsoe/ember-highcharts,CubiclDev/ember-highcharts