add a new feature

Example request

{
  "stac_version": "0.8.0",
  "type": "Feature",
  "id": "CS3-20160503_132130_04",
  "bbox": [
    -122.59750209,
    37.48803556,
    -122.2880486,
    37.613537207
  ],
  "geometry": {
    "type": "Polygon",
    "coordinates": [
      [
        [
          -122.308150179,
          37.488035566
        ],
        [
          -122.597502109,
          37.538869539
        ],
        [
          -122.576687533,
          37.613537207
        ],
        [
          -122.2880486,
          37.562818007
        ],
        [
          -122.308150179,
          37.488035566
        ]
      ]
    ]
  },
  "properties": {
    "datetime": "2016-05-03T13:21:30.040Z"
  },
  "links": [
    {
      "rel": "self",
      "href": "http://cool-sat.com/catalog/collections/cs/items/CS3-20160503_132130_04.json"
    }
  ],
  "assets": {
    "analytic": {
      "title": "4-Band Analytic",
      "href": "http://cool-sat.com/catalog/collections/cs/items/CS3-20160503_132130_04/analytic.tif"
    },
    "thumbnail": {
      "title": "Thumbnail",
      "href": "http://cool-sat.com/catalog/collections/cs/items/CS3-20160503_132130_04/thumb.png",
      "type": "image/png"
    }
  }
}