Version 1.9.13 fixed an issue in offline mode where if you ran `init_notebook_mode`

more than once the function would skip importing (because it saw that it had

already imported the library) but then accidentally clear plotly.js from the DOM.

This meant that if you ran `init_notebook_mode` more than once, your graphs would

not appear when you refreshed the page.

Version 1.9.13 solved this issue by injecting plotly.js with every iplot call.

While this works, it also injects the library excessively, causing notebooks

to have multiple versions of plotly.js inline in the DOM, potentially making

notebooks with many `iplot` calls very large.

Version 1.10.0 brings back the requirement to call `init_notebook_mode` before

making an `iplot` call. It makes `init_notebook_mode` idempotent: you can call

it multiple times without worrying about losing your plots on refresh.

- Fixed issue in offline mode related to the inability to reload plotly.js on page refresh and extra init_notebook_mode calls.