Bump version to 2.0.0-alpha

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Bump version to 1.8.6

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Sentinel 1.8.5

Sentinel 1.8.4

Sentinel 1.8.3

Sentinel 1.8.2

Sentinel 1.8.1

Update README.md

Signed-off-by: Eric Zhao <sczyh16@gmail.com>

Sentinel 1.7.2

Sentinel 1.7.1