Merge branch 'master' into 4.x-maintenance

Bump to version 4.2

Bump to 4.1

Fix classifiers

Merge branch 'master' into 3.x-maintenance

Bump to version 3.0

Bump to version 2.1

Fix README, "include" is "searchpath"

Bump to 1.5.2

Bump to version 1.5.1