Bump the minor version; new version is 1.5

PiperOrigin-RevId: 384317606
Change-Id: I1ddbd8b503073a65932582710558596b1b087246

Drop support for Python < 3.6, bump version to 1.4.

PiperOrigin-RevId: 357215926
Change-Id: I9828e12c7ae3fcfc86caeb74b18827e882855d10

Bump the minor version; new version is 1.3

PiperOrigin-RevId: 339897697
Change-Id: I26b06ab6ddfb105cfc3b515856faa8836e0cf40b

Increment version from 1.1 -> 1.2

Increment version from 1.0 -> 1.1

Initial stable version