Update jupyter_contrib_nbextensions to 0.4.0

[pyup-bot]

There's a new version of jupyter_contrib_nbextensions available.
You are currently using 0.3.3. I have updated it to 0.4.0

These links might come in handy: PyPI | Changelog | Repo

Changelog

0.4.0

---

Repo-level stuff:

• Require newer version of
  jupyter_nbextensions_configurator
  1197
  jcb91
• Remove version-pinning from lxml dependency
  1174
  codypiersall
• Use requirejs vs. require, to align with notebook usage
  1165
  gnestor
• tests specify exceptions (new flake8 moan)
  1143
  jcb91
• move js_highlight.py into nbconvert_support, specify exception type
  1140
  jcb91
• docs updates
  1200,
  1201
  jcb91

New features and bugfixes:

• livemdpreview new nbextension added!
  1155
  jcb91
• nbTranslate
  • Typos + readability improvements
    1191
    adyavanapalli,
  • Fix typo and revise text for better readability
    1190
    adyavanapalli,
  • use traitlets > 4.1 tag API
    1138
    jcb91
• collapsible_headings
  • indent heading collapse controls by level
    1183
    jcb91
  • patch TextCell.set_text to catch more changes
    1184
    jcb91
  • link complete font-awesome css from cdn, not just some fontfaces
    1179
    jcb91
• toc2
  • Add a 'download as HTML with toc' for Jupyter >= 5.1
    1182
    jfbercher
  • only set notebook dirty if metadata item changed
    1178
    jcb91
  • Bugfix undefined title_sidebar
    1175
    jfbercher
  • move config into toc2.js
    1167
    jcb91
  • configurable titles; dialog-alterable metadata settings
    1124
    jcb91
  • remove deprecated st var from template
    1199
    jcb91
  • [toc2] link complete font-awesome css from cdn
    1198
    jcb91
• scroll_down fix notebook 5.x compatibility
  1181
  jcb91
• exercise,exercise2 use bootstrap hidden class
  rather than jquery show/hide, in order to play nicely with collapsible_headings.
  fixes 990
  1169
  jcb91
• runtools don't alter selection when running cells
  1145
  jcb91
• ExecuteTime add preprocessor to execute notebook updating timing metadata
  1139
  jcb91
• snippets Updated README
  1150
  chuaxr
• code_prettify Update code_prettify.yaml
  1162
  fehiepsi

Got merge conflicts? Close this PR and delete the branch. I'll create a new PR for you.

Happy merging! 🤖