Safari compatibility (project file and basic demo)

[vheun]

• led and const are not supported by safari, for compatibility among all browsers they are replaced with var.
• Safari seems to handle the asynchronous loading process different then chrome and firefox. getAllEntries() needs to be called within onwriteend(), otherwise it produces an empty entry when a file is uploaded in Safari.

[clopez]

This likely fixes the issue i just reported? #46

[ebidel]

@clopez As you pointed out, the demo in master (http://rawgit.com/ebidel/idb.filesystem.js/master/demos/basic/) already works in Safari. It's html5-demos.appspot.com that needs to be updated.