Add method to enable in-app updates even if installed from market
Move canUpdateInMarket logic to UpdateManagerListener
Merge pull request #55 from hzsweers/develop

Add method to enable in-app updates even if installed from market
Fix potential NPE

NPE introduced through 33cc92093d2ed64ee28cd3975a3605a732081bd2 when registering update manager without listener.
Option to omit device identifier from crash log
Improve performance in listener checks

installedFromMarket() is more expensive than checking for the listener.