Version 0.4.3

Set version to 0.4.2

Update release notes for 0.4.1.

Update release notes for 0.4.0.

Zero-initialize the EXPLICIT_ACCESSW objects.

This may have fixed a segfault in winpty_open.

Fixes rprichard#80

Update the release notes for 0.3.0

Incorporate APPVEYOR_BUILD_NUMBER into the version number

Update the LICENSE copyright year

0.2.1 -- update VERSION and changelog

Add a RELEASES.md file and bump version to 0.2.0.