update changelog and make it easier to find

I just went to https://pypi.python.org/pypi/lockfile and noticed 0.11.0 was released (the last version I used was 0.10.2), so I want to see what's changed.

The long_description rendered to https://pypi.python.org/pypi/lockfile contains a "Documentation" link pointing to http://docs.openstack.org/developer/pylockfile but there's no changelog there. It also contains a "Source" link pointing to http://git.openstack.org/cgit/openstack/pylockfile but the RELEASE-NOTES file there hasn't been updated since 0.9.1 (see http://git.openstack.org/cgit/openstack/pylockfile/tree/RELEASE-NOTES).

There is also a lot of confusion caused by duplicate and unsynchronized content being scattered across a bunch of different places. For example, at the bottom of https://pypi.python.org/pypi/lockfile among the package metadata there is a "lockfile package documentation" link pointing to http://pythonhosted.org/lockfile/ which appears to be an abandoned instance of the sphinx html docs last updated for version 0.9.1. There's also https://github.com/smontanaro/pylockfile and https://github.com/openstack/pylockfile both of whose relationships to the other links are unclear.

Fixing these issues would go a long way toward improving the lockfile getting started experience. Thanks for your consideration.