Remove unused Header component

Author: AryanJ-NYC

package.json

@@ -17,7 +17,6 @@
     "axios": "^0.18.1",
     "docz": "^1.3.2",
     "docz-theme-default": "^1.2.0",
-    "gatsby": "^2.15.28",
     "prop-types": "^15.7.2",
     "react-helmet": "^5.2.1"
   },