Update toc for new jupyter book structure (#63)

Author: choldgraf

_toc.yml

@@ -1,16 +1,23 @@
 - file: README
-- file: jupyter-enhancement-proposal-guidelines/jupyter-enhancement-proposal-guidelines
 
-- header: Accepted
-- file: 44-xeus-incorporation/xeus-incorporation
-- file: 42-voila-incorporation/voila-incorporation
-- file: 29-jep-process/jep-process
-- file: 28-jupyter-server/jupyter-server
+- part: Information
+  chapters:
+  - file: jupyter-enhancement-proposal-guidelines/jupyter-enhancement-proposal-guidelines
+  - url: https://github.com/jupyter/enhancement-proposals/blob/master/jupyter-enhancement-proposal-guidelines/JEP-TEMPLATE.md
+    title: JEP Template
 
-- header: Implemented
-- file: 25-jupyter-enterprise-gateway-incorporation/jupyter-enterprise-gateway-incorporation
-- file: 22-jupyter-dashboards-deployment-attic/jupyter-dashboards-deployment-attic
-- file: 18-jupyter-declarativewidgets-incorporation/jupyter-declarativewidgets-extension-incorporation
-- file: 17-jupyter-dashboards-extension-incorporation/jupyter-dashboards-extension-incorporation
-- file: 12-jupyter-kernel-gateway-incorporation/jupyter-kernel-gateway-incorporation
-- file: 08-notebook-diff/notebook-diff
+- part: Accepted JEPs
+  chapters:
+  - file: 44-xeus-incorporation/xeus-incorporation
+  - file: 42-voila-incorporation/voila-incorporation
+  - file: 29-jep-process/jep-process
+  - file: 28-jupyter-server/jupyter-server
+
+- part: Implemented JEPs
+  chapters:
+  - file: 25-jupyter-enterprise-gateway-incorporation/jupyter-enterprise-gateway-incorporation
+  - file: 22-jupyter-dashboards-deployment-attic/jupyter-dashboards-deployment-attic
+  - file: 18-jupyter-declarativewidgets-incorporation/jupyter-declarativewidgets-extension-incorporation
+  - file: 17-jupyter-dashboards-extension-incorporation/jupyter-dashboards-extension-incorporation
+  - file: 12-jupyter-kernel-gateway-incorporation/jupyter-kernel-gateway-incorporation
+  - file: 08-notebook-diff/notebook-diff