Update grouped-categories.js

Updated deepClone function prevent infinite loop when final "category" property is an object.

Previously this function would only complete successfully if the final "category" property was an array of strings.
ie.
xAxis: {
   categories: [{
       name: "1 & 2 Broadgate",
       categories: ['Sub Category 1', 'Sub Category 2']
   }...

This change allow it also to accept objects within final category layer:
xAxis: {
   categories: [{
       name: "Category 1",
       categories: [{ name: "Sub Category 1" }, { name: "Sub Category 2" }]
   }...
Merge pull request #25 from BrianXerri/master

Update grouped-categories.js deepClone function
Different options for each level. Closes #26.

Now each level has own subset of styles, like rotation or font styles.
Use group visibility, not label itself [t:27]
Remove jQuery requirement from plugin

Added HighchartsAdapter requirement.
Merge remote-tracking branch 'origin/master' into gh-pages
Add stroke-width for 4.0.3 compatibility. Closes #30.
Merge remote-tracking branch 'origin/master' into gh-pages
Merge remote-tracking branch 'origin/master' into gh-pages