Urgent fix the link error in the README.rst
Urgent fix the link error in the README.rst

The devstack installation guide linke is not able to access,
for the link path is incorrect, it should be
https://github.com/openstack/tricircle/blob/master/doc/source/installation.rst
instead.

Change-Id: I377abf8e77637f82e55f4a4613d4a9c2224c15b0
Signed-off-by: Chaoyi Huang <a9255ab284bb421be02744591ccbe1d599fb05d5@huawei.com>

stackforge/tricircle,stackforge/tricircle,openstack/tricircle,openstack/tricircle