0.9.1 - breaking changes bringing closer to 1.0

Improve readme further.

Fix pylint errors

BUG=None
TEST=make lint
TEST=tools/edidparser
TEST=tools/jsonedid
TEST=tools/jsonparser
TEST=utils/screenshot

Change-Id: If351972e01c2f25de1cb24613b88a0af8311a6c5
Reviewed-on: https://chromium-review.googlesource.com/223104
Tested-by: Wai-Hong Tam <[email protected]>
Reviewed-by: Hung-ying Tyan <[email protected]>
Commit-Queue: Wai-Hong Tam <[email protected]>