Update configuration process

[colin-marshall]

@olefredrik and others, I have found it to be a pain that entering in the proxy URL for browsersync shows up in git as changes, so I have to remember to remove it whenever I make changes to the gulpfile to push upstream. I noticed you have had to undo some commits for the same reason in your PR's.

I propose the following:

• Add config-default.yml file to the repo (just a duplicate of config.yml)
• Add config.yml to .gitignore and remove it from tracking in repo
• In the gulpfile, if config.yml exists, load the configuration from config.yml. If config.yml does not exist, load configuration from config-default.yml.
• Move the browsersync proxy URL from the gulpfile to the config file.

This way users can create their own config.yml file by copying config-default.yml and have the theme configured differently for different environments and not deal with git headaches (like the proxy URL change showing up in git).

What do you guys think?

[olefredrik]

Good stuff, @colin-marshall ! Let's to this 👍