Release 0.5.0

Version 0.5.0 provides several bug fixes and improvements leading to higher quality.

• Global JS object window.plugins. indexAppContent is only available when running on iOS
• JS function isIndexingAvailable was added
• JS function init is not needed anymore (but available to ensure compatibility)
• JS function setIndexingInterval accepts 0 as numeric input
• JS function setIndexingInterval comes into affect immediately and not after previous index interval expired
• Compatibility ensured with other plugins like cordova-universal-links which implement iOS UIApplicationDelegate method application:continueUserActivity:restorationHandler
• Unit/Integration tests added
• Continuous Integration via Travis CI
• Improved documentation