in `nbextensions/config/main`:  * relax requirements for nbextension yaml descriptor files, removing absolute requirement for `Compatibility` and `Description` keys
in `nbextensions/config/main`:
 * relax requirements for nbextension yaml descriptor files, removing absolute requirement for `Compatibility` and `Description` keys

benvarkey/IPython-notebook-extensions,ipython-contrib/IPython-notebook-extensions,jcb91/IPython-notebook-extensions,juhasch/IPython-notebook-extensions,ipython-contrib/IPython-notebook-extensions,jbn/IPython-notebook-extensions,jbn/IPython-notebook-extensions,jcb91/IPython-notebook-extensions,ipython-contrib/IPython-notebook-extensions,benvarkey/IPython-notebook-extensions,juhasch/IPython-notebook-extensions,andyneff/IPython-notebook-extensions,andyneff/IPython-notebook-extensions,andyneff/IPython-notebook-extensions,benvarkey/IPython-notebook-extensions,juhasch/IPython-notebook-extensions,jbn/IPython-notebook-extensions,jbn/IPython-notebook-extensions,jcb91/IPython-notebook-extensions,andyneff/IPython-notebook-extensions,ipython-contrib/IPython-notebook-extensions,benvarkey/IPython-notebook-extensions