Improve JS bindings

Summary:
- Fix a few things related to how npm should publish the package (sources were in the gitignore file, so I think it would have break the build during install - I fixed this by adding a npmignore that should override the gitignore rules)

- The enumerations values are now generated directly from `enums.py`

- I added percent unit support (#258) to the bindings (`.setWidthPercent` is currently exposed, but I've also added a very very little parsing to also support `.setWidth("100%")` and `.setWidth(.getWidth())`), added the missing tests, and fixed Travis.
Closes https://github.com/facebook/yoga/pull/314

Reviewed By: mikearmstrong001

Differential Revision: D4377198

Pulled By: emilsjolander

fbshipit-source-id: 774dfafd416f5421f3be59a1d181eb7056487abe

javascript/sources/YGEnums.js

@@ -0,0 +1,91 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+module.exports = {
+
+  FLEX_DIRECTION_COUNT: 4,
+  FLEX_DIRECTION_COLUMN: 0,
+  FLEX_DIRECTION_COLUMN_REVERSE: 1,
+  FLEX_DIRECTION_ROW: 2,
+  FLEX_DIRECTION_ROW_REVERSE: 3,
+
+  MEASURE_MODE_COUNT: 3,
+  MEASURE_MODE_UNDEFINED: 0,
+  MEASURE_MODE_EXACTLY: 1,
+  MEASURE_MODE_AT_MOST: 2,
+
+  PRINT_OPTIONS_COUNT: 3,
+  PRINT_OPTIONS_LAYOUT: 1,
+  PRINT_OPTIONS_STYLE: 2,
+  PRINT_OPTIONS_CHILDREN: 4,
+
+  EDGE_COUNT: 9,
+  EDGE_LEFT: 0,
+  EDGE_TOP: 1,
+  EDGE_RIGHT: 2,
+  EDGE_BOTTOM: 3,
+  EDGE_START: 4,
+  EDGE_END: 5,
+  EDGE_HORIZONTAL: 6,
+  EDGE_VERTICAL: 7,
+  EDGE_ALL: 8,
+
+  POSITION_TYPE_COUNT: 2,
+  POSITION_TYPE_RELATIVE: 0,
+  POSITION_TYPE_ABSOLUTE: 1,
+
+  DIMENSION_COUNT: 2,
+  DIMENSION_WIDTH: 0,
+  DIMENSION_HEIGHT: 1,
+
+  JUSTIFY_COUNT: 5,
+  JUSTIFY_FLEX_START: 0,
+  JUSTIFY_CENTER: 1,
+  JUSTIFY_FLEX_END: 2,
+  JUSTIFY_SPACE_BETWEEN: 3,
+  JUSTIFY_SPACE_AROUND: 4,
+
+  DIRECTION_COUNT: 3,
+  DIRECTION_INHERIT: 0,
+  DIRECTION_LTR: 1,
+  DIRECTION_RTL: 2,
+
+  LOG_LEVEL_COUNT: 5,
+  LOG_LEVEL_ERROR: 0,
+  LOG_LEVEL_WARN: 1,
+  LOG_LEVEL_INFO: 2,
+  LOG_LEVEL_DEBUG: 3,
+  LOG_LEVEL_VERBOSE: 4,
+
+  WRAP_COUNT: 2,
+  WRAP_NO_WRAP: 0,
+  WRAP_WRAP: 1,
+
+  OVERFLOW_COUNT: 3,
+  OVERFLOW_VISIBLE: 0,
+  OVERFLOW_HIDDEN: 1,
+  OVERFLOW_SCROLL: 2,
+
+  EXPERIMENTAL_FEATURE_COUNT: 2,
+  EXPERIMENTAL_FEATURE_ROUNDING: 0,
+  EXPERIMENTAL_FEATURE_WEB_FLEX_BASIS: 1,
+
+  ALIGN_COUNT: 5,
+  ALIGN_AUTO: 0,
+  ALIGN_FLEX_START: 1,
+  ALIGN_CENTER: 2,
+  ALIGN_FLEX_END: 3,
+  ALIGN_STRETCH: 4,
+
+  UNIT_COUNT: 3,
+  UNIT_UNDEFINED: 0,
+  UNIT_PIXEL: 1,
+  UNIT_PERCENT: 2,
+
+};