[Bug][Jupyter Widget] Tooltip doesn't show the selected columns in hexbin

**Describe the bug**
Tooltip doesn't show the selected columns in hexbin

**To Reproduce**
Steps to reproduce the behavior:
1. load kepler
2. Add data & config
3. Export map
4. Use hexbin
5. Try adding columns into tooltip

**Expected behavior**
the tooltip columns should work no matter what viz we select

**Screenshots**
If applicable, add screenshots to help explain your problem.

**Environment (please complete the following information):**
- Python version: py3.6
- keplergl Widget version [e.g. 0.1.0]

**Additional context**