Update the troveclient's README.
Update the troveclient's README.

Change the display of documentation and bugs, update some url from
http to https

Change-Id: Iab61ffabfa00ef1d265c6ea84ac0e863448bc829
Signed-off-by: zhanggang <fc3878963d7a7a907bb5027f7ef4c10c7cbd6f68@cmss.chinamobile.com>

openstack/python-troveclient,openstack/python-troveclient