Ensure fileData is actually copied when reading uncompressed zip files

On pre-10.9 systems, [NSData copy] returns the same object, see rdar://14670403. Using [NSData dataWithBytes:length:] always creates a new object.

Create data objects using "alloc"/"init" instead of "data" to avoid autorelease pools not getting drained quickly.

Minor style fix.
Merge branch 'master' of https://github.com/goetzf/zipzap into goetzf_master