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
Merge branch 'clean-up-gitignore' into staging

* clean-up-gitignore:
  Clean up and alphabetize gitignore
  .DS_Store should ignore all .DS_Store files
 MIL-419 Added youtube embed URL to jekyll front matter
Merge pull request #27 from aravind666/content-migration

 MIL-419 Added youtube embed URL to YAML front matter of messages and video posts
Remove vendor prefixes
Merge branch 'MIL-276' into staging
Add and update utility classes
Update style to include new utility classes
MIL-344 add demo modal window
MIL-414_address_modal finish up modal
MIL-347 serve pages
icons