Drop non-standard object API in favor of ES5 one
Fix errors caused by the api change

Move isFile/isDirectory into the prototype too.
Move the is* properties up the prototype chain

IE only saves properties which are at the top of the property chain.
Removes unnecessary getter/setter
Implement isFile/isDirectory to ES5 getters

The enumerable attribute makes it possible to save the attribute in
IndexedDB.
Make blob_ enumerable too
Merge pull request #13 from Sebmaster/fix-ie

Fix IE10