Additional playback callbacks

fix for RN 0.24+

[iOS] Added orientation to onLoad event.

README: prevent blocking outside music

fix screenPhysicalPixels error

[Podspec] Set podspec version from the package.json and fix git source in the Podspec

Support fullscreen mode

Add naturalSize to callback

Update README to explain where android assets go

[Podspec] Read version from the package.json, add author, add tag to the git source, add .git extension