Selectr is not idempotent

[rnickmccandless]

When instantiating an instance of new Selectr(element) with the same element multiple times, Selectr generates new HTML markup resulting in duplicating drop downs.

Unexpected result:

This was first noticed when using Turbolinks while navigating the website forward, then back.

* I understand that at this time, the project is not being maintained. Hopefully this project will see a new maintainer soon since Selectr has been a great simple way to apply a better select element.

[Xaraxia]

I've worked around this problem by detecting the classes on the underlying element, and not making the Selectr call if it doesn't exist. Suboptimal, yes, but it works.