FileReader events aren't zoned

[robwormald]

Ref: angular/angular#2533

Failing spec PR: #136

It appears that the doing using reader.addEventListener('loadend', function(... works, but doing the equivalent with reader.onloadend etc isn't captured properly.

[btford]

👍

[matthewjh]

@robwormald @btford, please take a look at #174 where I have attempted to fix this.