bump version to v0.16b2
# 1. bug fix release beta0: VERSION = "0.9.1b0"; version = (0, 9, 1, 'b0')
# 2. bug fix release: VERSION = "0.9.2"; version = (0, 9, 2, 'release')
-version = (0, 16, 0, 'b1')
-__version__ = "0.16b1"
+version = (0, 16, 0, 'b2')
+__version__ = "0.16b2"
