[VTA][HotFix] Relay->VTA quantization fix (apache#4433)

* relay -> vta fix

* setting optlevel to 3 for quantization to fold batchnorm

Fix issue mutating if expressions (apache#2601)

(cherry picked from commit f6be4d6)

release 0.4

v0.3 release

[RELEASE] Release note for 0.2 (apache#853)

[DOC] Add link to release blog (apache#342)