Preparing for release of version 3.5.2

prepare 3.5.1 release (launchdarkly#119)

prepare 3.5.0 release (launchdarkly#116)

prepare 3.4.1 release (launchdarkly#110)

prepare 3.4.0 release (launchdarkly#109)

prepare 3.3.0 release (launchdarkly#108)

fix version string (launchdarkly#107)

version 3.2.0

prepare 3.1.0 release (launchdarkly#95)

prepare 3.0.0 release (launchdarkly#94)