Fix exclude deletion of html files in public/static during bootstraping (#2600)
Fix exclude deletion of html files in public/static during bootstraping (#2600)

As mentioned in https://www.npmjs.com/package/del#beware the parent
folder should be excluded since the blog ** pattern matches all children
and the parent.
fk/gatsby,danielfarrell/gatsby,ChristopherBiscardi/gatsby,0x80/gatsby,gatsbyjs/gatsby,fabrictech/gatsby,mingaldrichgan/gatsby,fk/gatsby,Khaledgarbaya/gatsby,Khaledgarbaya/gatsby,mingaldrichgan/gatsby,danielfarrell/gatsby,ChristopherBiscardi/gatsby,ChristopherBiscardi/gatsby,gatsbyjs/gatsby,mingaldrichgan/gatsby,ChristopherBiscardi/gatsby,fabrictech/gatsby,gatsbyjs/gatsby,fk/gatsby,gatsbyjs/gatsby,fabrictech/gatsby,0x80/gatsby,gatsbyjs/gatsby,0x80/gatsby,danielfarrell/gatsby,Khaledgarbaya/gatsby,gatsbyjs/gatsby