Nncase

Major changes
- Add L2 based calibration methods
- Support Slice
- Support Mac OS
Bugs fixes
- Fix a bug when compiling multiple outputs model on Linux

Tips
- Beta2 version support **tflite** and **caffe** importer

Major changes
- Add quantized version of Conv2D, MatMul, Binary, ResizeImage ops
- Add Conv2DTranspose op
- Add best fit memory allocation solver (enabled by default, see [usage](https://github.com/kendryte/nncase/tree/master/docs/USAGE.md))
- Update documentation
Bugs fixes
- Fix a bug in TFLite Softmax lowering

Tips
- Beta1 version support **tflite** and **caffe** importer

Major changes
- Add tflite ops lowering: Relu LeakyRelu Logistic
Bugs fixes
- Fix a bug in strided slice codegen
- Fix reduce axis calculation
- Fix shape getter in tflite importer

Tips
- Alpha2 version only support **tflite** importer

Major changes
- Rewrite in C++
- Generate kmodel v4
- Support more ops

Tips
- Alpha1 version only support **tflite** importer

Breaking changes
- Generate kmodel v2
Major changes
- Add max/average pool 2x2 with stride=1/2 and 4x4 with stride=4 for K210
- Add 16bits weights quantization
- Fix segmentation fault on linux

Major changes
- Add K210 emulator
- Support float inference type