Travis tweaks. Setting which matrix builds are allowed to fail. Adding android api level 24 emulator.
Travis tweaks. Setting which matrix builds are allowed to fail. Adding android api level 24 emulator.

Countly/countly-sdk-android,Countly/countly-sdk-android,Countly/countly-sdk-android,Countly/countly-sdk-android,Countly/countly-sdk-android