[Bug][Jupyter Widget]: dev install gives Uncaught Error: Could not find "store"

**Describe the bug**
Dev install does not produce a working nbextension, upon creating a widget view, the js dev console gives:
```
Uncaught Error: Could not find "store" in the context of "Connect(Container)". Either wrap the root component in a , or pass a custom React context provider to and the corresponding React context consumer to Connect(Container) in connect options.
```

Note that creating the widget works, but looking at the code it seems you only create the kepler object when the view is created:

**To Reproduce**
* clone master
* follow dev install instructions
* execute
```
from keplergl import KeplerGl
map_1 = KeplerGl(height=400)
```
* create a view `display(map_1)` (now the error comes)

**Expected behavior**
A clear and concise description of what you expected to happen.

**Environment (please complete the following information):**
```
$ node --version dev
v12.11.1
$ npm --version dev
6.11.3
$ yarn --version dev
1.21.1
```