Check sidebar conditional tag exists

Return false for non-existent conditional tags. Fixes #993
Merge pull request #1113 from roots/conditional_checks

Check sidebar conditional tag exists
Runs platform agnostic postinstall. Closes #1078

Global node binary is used to execute bower.
Global grunt binary (from grunt-cli) is used to run `dev` task.
updated package.json to use version 1.3.9 or greater
Merge pull request #1118 from LibLogic/master

updated package.json to use version 1.3.9 or greater
Only load GA in production environment

Loads Google Analytics when `WP_ENV` is 'production'
Otherwise it passes `ga()` arguments as an array to `console.log()`

Also sets cookie domain to be auto configured.
Always load GA snippet when not in production
Remove Grunt badge
Merge remote-tracking branch 'upstream/master'