Usage of valueOf is better
Merge branch 'master' of github.com:soomla/android-store

* 'master' of github.com:soomla/android-store:
  Update documentation.md
  Update documentation.md
  Update documentation.md
  Changed documentation: him -> him/her, etc..
- Separated restore transactions from refresh
  market items details.
- New event MarketItemsRefreshStarted
- Changed event name: MarketItemsRefreshFinished
Extracted an abstract class "IabHelper" so we can
create more IabHelpers.
Google's IabHelper is now called GoogleIabHelper.
[WIP] implementing Amazon IAP
Finished support for multiple billing providers.
Tested Amazon and Google play. They work.
fixed submodules
Amazon IAB service is now in a different repo
Showing initialization of Google Play IAB Service
Showing initialization of Google Play IAB Service
Added Amazon billing service jar to the repo
Finished work on Amazon and Google Play integrations
Fixed library project to not include google play sources
logDebug is default to false
Fixed documentation
fixed license in files