Python 2 support, spec update, missing npm dependency

Author: SylvainCorlay

ipywidgets/widgets/widget_upload.py

@@ -90,7 +90,7 @@ def __init__(self,
         self.compress_level = compress_level
         self.value = {}
 
-        super().__init__()
+        super(FileUpload, self).__init__()
 
     @validate('compress_level')
     def _valid_compress_level(self, proposal):

packages/controls/package-lock.json

@@ -67,6 +67,7 @@
     "karma-webpack": "^2.0.3",
     "mocha": "^3.3.0",
     "npm-run-all": "^1.5.1",
+    "pako": "^1.0.10",
     "postcss-cli": "^4.1.0",
     "postcss-cssnext": "^3.0.2",
     "postcss-import": "^10.0.0",

packages/controls/package.json

@@ -345,6 +345,31 @@ Attribute        | Type             | Default          | Help
 `layout`         | reference to Layout widget | reference to new instance | 
 `style`          | reference to DescriptionStyle widget | reference to new instance | Styling customizations
 
+### FileUploadModel (@jupyter-widgets/controls, 1.4.0); FileUploadView (@jupyter-widgets/controls, 1.4.0)
+
+Attribute        | Type             | Default          | Help
+-----------------|------------------|------------------|----
+`_counter`       | number (integer) | `0`              | 
+`_dom_classes`   | array of string  | `[]`             | CSS classes applied to widget DOM element
+`_model_module`  | string           | `'@jupyter-widgets/controls'` | 
+`_model_module_version` | string           | `'1.4.0'`        | 
+`_model_name`    | string           | `'FileUploadModel'` | 
+`_view_module`   | string           | `'@jupyter-widgets/controls'` | 
+`_view_module_version` | string           | `'1.4.0'`        | 
+`_view_name`     | string           | `'FileUploadView'` | 
+`accept`         | string           | `''`             | Type of files the input accepts. None for all. See https://developer.mozilla.org/en-US/docs/Web/HTML/Element/input#attr-accept
+`compress_level` | number (integer) | `0`              | Compress level: from 1 to 9 - 0 for no compression
+`description`    | string           | `''`             | Description of the control.
+`description_tooltip` | `null` or string | `null`           | Tooltip for the description (defaults to description).
+`disabled`       | boolean          | `false`          | Enable or disable button
+`error`          | string           | `''`             | Error message
+`layout`         | reference to Layout widget | reference to new instance | 
+`li_content`     | array            | `[]`             | List of file content (bytes)
+`li_metadata`    | array            | `[]`             | List of file metadata
+`multiple`       | boolean          | `false`          | If true, allow for multiple files upload, else only accept one
+`style`          | reference to DescriptionStyle widget | reference to new instance | Styling customizations
+`style_button`   | string           | `''`             | Optional style for button (label element)
+
 ### FloatLogSliderModel (@jupyter-widgets/controls, 1.4.0); FloatLogSliderView (@jupyter-widgets/controls, 1.4.0)
 
 Attribute        | Type             | Default          | Help