Merge pull request #121 from openexr/develop

v2.2.0 ready for release
Add dwa test images to dist (tarball) manifest.
Also drop README.win32 from tarball.  (Already removed from repo.)

[New Cmake-centric instructions covering builds for Windows and other
platforms to follow.]
Merge pull request #127 from openexr/tarball_contents_fix

Tarball contents fix