Bump the version to 0.2.0

Signed-off-by: Jia Zhang <zhang.jia@linux.alibaba.com>

CHANGELOG

+# 2020-06-30 v0.2.0
+- Integrate new components shim-rune and runectl.
+- Implement Enclave Runtime PAL API v2.
+- Change to load the Enclave Runtime PAL on host side.
+- Refresh skeleton example with enclave call ABI.
+
+---
+
+# 2020-05-15 v0.1.0
+- Initial implementation of OCI Runtime.

VERSION

-0.1.0
+0.2.0
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