docs: karbor README.rst title overline and underline too short

[Yuval Brik]

In karbor's README.rst, the main title overline and underline are too short.
That causes https://pypi.python.org/pypi/karbor to look unformatted.

You can validate it passes lint using on of the following:
https://github.com/twolfson/restructuredtext-lint
https://github.com/collective/collective.checkdocs

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/403713

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/403713
Committed: https://git.openstack.org/cgit/openstack/karbor/commit/?id=e8000883ef5eb04addd79a99921e12b6a9cd2029
Submitter: Jenkins
Branch: master

commit e8000883ef5eb04addd79a99921e12b6a9cd2029
Author: Tin Lam <email address hidden>
Date: Mon Nov 28 07:51:52 2016 -0600

    Corrected README.rst overline and underline issue

    Running rst-lint on README.rst currently results in the warning:
    "WARNING README.rst:10 Title overline too short." This patch set
    corrects the warning.

    Also, this patch set removes extra space at EOL.

    TrivialFix
    Closes-Bug: #1645279

    Change-Id: I48ea3ec73346da3b27c093dc9135aa19ff4b623f