!26 Update release notes for r0.5

Merge pull request !26 from chengbin/r0.5

RELEASE.md

-## Initial Version
-- Upload the initial framework
-- Basic support for Ascend910 platform
-- Integration with GraphKernel
+# Release 0.5.0-beta
+## Major Features
+* Support auto-schedule and code-generation on Ascend platform.
+* Provide C++ APIs of basic operators used in MindSpore.
+* Support Elementwise-Elementwise, Reduce-Elementwise fusion patterns in Bert.
+* Support LambUpdateWithLR, LambNextMv, BatchMatmul optimazition for Bert.
+
+# Initial Version
+* Upload the initial framework.
+* Basic support for Ascend910 platform.
+* Integration with GraphKernel.