Delete OpsetVersionConverter.md which is a duplicate of VersionConverter.md (onnx#1818)

* Delete OpsetVersionConverter.md

* update link to versionconverter.md

* Update VersionConverter.md

* Update VersionConverter.md

Author: prasanthpul

README.md

@@ -25,7 +25,7 @@ ONNX is [widely supported](http://onnx.ai/supported-tools) and can be found in m
 # Programming utilities for working with ONNX Graphs
 * [Shape and Type Inference](docs/ShapeInference.md)
 * [Graph Optimization](docs/Optimizer.md)
-* [Opset Version Conversion](docs/OpsetVersionConverter.md)
+* [Opset Version Conversion](docs/VersionConverter.md)
 
 # Contribute
 ONNX is a community project. We encourage you to join the effort and contribute feedback, ideas, and code.

docs/OpsetVersionConverter.md

@@ -1,16 +1,11 @@
 # ONNX Version Converter
 
-ONNX provides a C++ library for converting ONNX models between different
-opset versions. The library leverages the convenient in-memory
-representation that is much more convenient to manipulate than the raw
-protobuf structs, and converters to and from the protobuf format which
-were developed for the ONNX Optimizer.
-
-The primary motivation is to improve backwards compatibility of ONNX
+ONNX provides a library for converting ONNX models between different
+opset versions. The primary motivation is to improve backwards compatibility of ONNX
 models without having to strengthen the spec for ONNX backends.  This
 allows backend developers to offer support for a particular opset version
 and for users to write or export models to a particular opset version but
-run in an environment with a different opset version.
+run in an environment with a different opset version. Implementation wise, the library leverages the in-memory representation that is much more convenient to manipulate than the raw protobuf structs, and converters to and from the protobuf format which were developed for the ONNX Optimizer.
 
 You may be interested in invoking the provided op-specific adapters, or in
 implementing new ones (or both). Default adapters only work in the default
@@ -19,7 +14,9 @@ conversion methods, dependent on the nature of relevant breaking changes.
 
 ## Invoking The Version Converter
 
-The version converter may be invoked either via C++ or Python. The Python API
+The version converter may be invoked either via C++ or Python. 
+
+The Python API
 is described, with example,
 [here](PythonAPIOverview.md#converting-opset-version-of-an-onnx-model).
 
@@ -38,7 +35,7 @@ is the result of apply all relevant adapters between initial_version and
 target_version. For a list of available passes, see
 [convert.h](onnx/version_converter/convert.h).
 
-Implementing Adapters
+## Implementing Adapters
 
 You can implement a new adapter by subclassing `Adapter`, and registering
 your new adapter with `VersionConverter::registerAdapter()`. Adapters operate