Recently added organization members

[Colin Walters <walters verbum org>]

Hi, I have recently invited a few new people to be members of the "ostreedev" github organization; this means 
they have the rights to use "r+" to merge pull requests.

- wmanley (stb-tester.com)
- sinnykumari (Red Hat)
- rfairley (Red Hat)

Additionally, pwithnall (Endless) is now a full owner; I've known him for a long time and he's contributed 
quite a bit to the OSTree codebase so far, and I want to be sure that the capability to e.g. add members is 
spread around a bit between contributing companies.

In general, while a few of us who are employed by Red Hat generally will have time to respond to pull 
requests fairly quickly, I'd love if more people felt free to at least drop a "LGTM" on pull requests and do 
so some review.  Particularly if you're planning to contribute some to libostree!

Review is a tricky subject I know; use your best judgement.  If someone is e.g. adding new API, that's 
something where it'd be good if a "core" reviewer was able to handle it (in addition to one or more optional 
non-merging "LGTM"s as above)  But if it's a memory leak, documentation fix or whatever - don't hesitate to 
merge.

At some point in the future I'd like to enhance our CI so we have an "auto-assignment" bot like the 
https://github.com/rust-highfive bot - this would also happen with a move to Prow: 
https://github.com/kubernetes/test-infra/tree/master/prow

Thanks again to everyone who has contributed so far, and keep the reviews and patches coming!