Update plotting data notebook with interface changes (#400)

* Update plotting data notebook with interface changes

This commit updates the tutorial notebook for plotting data with updates
to the interface being made in Qiskit/qiskit#1359 . The changes
made in that PR will reflect the stable interface of the plotting data
functions documented here. So we'll have to update the notebook before
the release.

* Finishing Touches

* Regenerate to get histogram legend fix

Author: mtreinish

index.ipynb

@@ -133,7 +133,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.6.7"
+   "version": "3.7.1"
   }
  },
  "nbformat": 4,