Added a route to the API that will get vlans for a given device

/api/v0/vlans/:hostname will list vlans for a device:

{
 "status": "ok",
 "count": 2,
 "vlans": [
  {
   "vlan_vlan": "1",
   "vlan_domain": "1",
   "vlan_name": "Testing VLAN",
   "vlan_type": "ethertype",
   "vlan_mtu": "1500"
  },
  {
   "vlan_vlan": "2",
   "vlan_domain": "1",
   "vlan_name": "Work VLAN",
   "vlan_type": "ethertype",
   "vlan_mtu": "1500"
  }
 ]
}