Update custom_plugins.rst

add a description to show a foreign key relation in the edit mode of a plug in. May be i am wrong but i didn't found a other way to show the relation in the inline admin.
Removed references to 'meta_keywords' since it was removed in 3.x
Pin selenium version
Merge pull request #3195 from yakky/test/selenium_py3

Damn the torpedoes full speed ahead
Pin selenium version
Merge branch 'develop' of https://github.com/kater169/django-cms into kater169-develop
Fix #3189, get_plugins_for_page didn't resolve inherited template the right way
Fix formatting issues
Merge pull request #3187 from jsma/develop

Removed references to 'meta_keywords' since it was removed in 3.x
Update custom_plugins.rst

tiny typo
Merge pull request #3196 from yakky/feature/fix_plugin_rst

Update custom_plugins.rst
Merge pull request #3190 from johnraz/Issue3189-fix-get_plugins_for_page

Issue3189 fix get plugins for page
Merge pull request #3197 from yakky/kater169-develop

Update custom_plugins.rst