Can't call repr on a Checklist

[rmarren1]

You can call repr on every dash core component except for Checklist. It crashes with a maximum recursion error. This has been happening since 0.12.0 (I didn't look further back).

To reproduce, simply

python
>>> import dash_core_components as dcc
>>> dcc.Checklist()

This is super weird, I can't think of a reason that Checklist is special, other than that it is the first components. All of the components are built the same way.

[chriddyp]

my guess is that it's related to this: #133