Updating _config_dev.yml to match changes to root and repo vars

#------------------------------------------------------------

# This config-file is only needed for development. Instead of changing

# the url everytime you work locally on the project, run a server with

# This config file is only needed for development. Instead of changing

# the URL everytime you work locally on the project, run a server with

# both configuration files:

#

#    jekyll serve --config _config.yml,_config_dev.yml

#------------------------------------------------------------

# Is this production or development? (Overrides _config.yml.)

is_production: false

# Override root so that CSS and other resources will load locally.

github:

  url: http://0.0.0.0:4000

root: http://localhost:4000