Release 150707

isPushNotificationsSupported uses features detection instead of userAgent

• isPushNotificationsSupported now uses detection by checking for browse features instead of using a userAgent whitelist.
• This enables support for the UC Browser.
• This fixes Samsung Internet compatibility with HTTP sites
• Reduction in size of OneSignalSDK.js shim from 17.1KiB to 8.4KiB (before gzip)
• Other misc small clean up of REST API params and browser detection code
• Changes done in PR #541 & #543