Add Apache SINGA to frameworks (onnx#122)

Author: moazreyad

README.md

@@ -23,6 +23,7 @@
 | [Apache MXNet](http://mxnet.incubator.apache.org/) | part of mxnet package [docs](http://mxnet.incubator.apache.org/api/python/contrib/onnx.html) [github](https://github.com/apache/incubator-mxnet/tree/master/python/mxnet/contrib/onnx) | [Exporting](tutorials/MXNetONNXExport.ipynb) | [Importing](tutorials/OnnxMxnetImport.ipynb) |
 | [PyTorch](http://pytorch.org/) | [part of pytorch package](http://pytorch.org/docs/master/onnx.html) | [Exporting](tutorials/PytorchOnnxExport.ipynb), [Exporting - Different ONNX Opsets](tutorials/ExportModelFromPyTorchToDifferentONNXOpsetVersions.md), [Extending support](tutorials/PytorchAddExportSupport.md) | coming soon |
 | [SciKit-Learn](http://scikit-learn.org/) | [onnx/sklearn-onnx](https://github.com/onnx/sklearn-onnx) | [Exporting](http://onnx.ai/sklearn-onnx/index.html) | n/a |
+| [Apache SINGA](http://singa.apache.org/) | [built-in](https://github.com/apache/incubator-singa/blob/master/python/singa/sonnx.py) | [Exporting](https://github.com/apache/incubator-singa/tree/master/examples/onnx) [experimental]| [Importing](https://github.com/apache/incubator-singa/tree/master/examples/onnx) [experimental] |
 | [TensorFlow](https://www.tensorflow.org/) | [onnx/onnx-tensorflow](https://github.com/onnx/onnx-tensorflow) and [onnx/tensorflow-onnx](https://github.com/onnx/tensorflow-onnx) | [Exporting - ONNX-Tensorflow](tutorials/OnnxTensorflowExport.ipynb)<br>[Exporting - Tensorflow-ONNX](https://github.com/onnx/tensorflow-onnx/blob/master/examples/call_coverter_via_python.py) | [Importing](tutorials/OnnxTensorflowImport.ipynb) [experimental] |
 | [TensorRT](https://developer.nvidia.com/tensorrt) | [onnx/onnx-tensorrt](https://github.com/onnx/onnx-tensorrt) | n/a | [Importing](https://github.com/onnx/onnx-tensorrt/blob/master/README.md) |