Increment version

[crusaderky]

FYI @honnibal due to the introduction of nighly builds, it would be best from now on

• immediately before a release, bump version to the release version and remove the dev marker, e.g. from 1.3.4.dev0 to 1.3.4
• immmediately after a release, bump version again to re-add the dev marker, e.g. 1.3.5.dev0

Alternatively to the above the project could switch to SCM versioning