Allow multiple treeviews in a single app to be configured differently

[wr0ngway]

It would be nice if one had a way to configure multiple tree views differently, e.g. twistieTemplates
I'm new to angular, so this could just be ignorance on my part, but it seems like a number of items in the config are global for all tree views.

[jtrussell]

For some options (like twistie templates) there's no good way to do this at the moment. For others you can use element level attributes (like ivh-treeview-use-checkboxes) to customize different treeview instances.

Being able to customize all options independently seems like a reasonable feature to add though, perhaps through an ivh-treeview-options attribute, so I'm going to stick it on v1.0.0 roadmap. Thanks!