Release 0.6.0

This release commits to SONAME stability on patch releases (for versions 0.x) and on minor releases (for versions after 1.x). The release version is set to 0.6.0 (and therefore the SONAME to 0.6) because the SONAME of the previous release is 0.5.0.

• PR#177: set SONAME to major/minor after/before 1.x. See #176.