Set broswerSync to only run with a flag
Don't start browserSync unless sync flag is passed
Change PORT var accordingly with sync option
Remove specific ad-button
Add billboard style to kitchen sink
Remove unused dependency
Raise errors when configuration values are missing

I was having a lot of difficulty debugging why I was not able to sign 
in to the website. The issue came down to the fact that I was missing 
my .env file. The configuration object now exports an interface that 
checks for the presence of the configuration key.
.DS_Store should ignore all .DS_Store files
Clean up and alphabetize gitignore
 MIL-419 Added youtube embed URL to jekyll front matter
Remove vendor prefixes
button styling for events list
MIL-347 Finish up events page