Bump version to v2.0.0rc4 (open-mmlab#2559)

Bump version to v1.7.1 (open-mmlab#2516)

Bump version to v2.0.0rc3 (open-mmlab#2447)

Bump version to v1.7.0 (open-mmlab#2362)

* Bump version to v1.7.0

* remove deprecated message

Bump version to v2.0.0rc2 (open-mmlab#2349)

* Bump version to v2.0.0rc2

* minor refine

Bump version to v1.6.2 (open-mmlab#2285)

Bump version to v2.0.0rc1 (open-mmlab#2240)

bump version to v1.6.1 (open-mmlab#2142)

Bump version to v1.6.0 (open-mmlab#2096)

* bump version to v1.6.0

* minor fix

Bump version to v1.5.3 (open-mmlab#2053)