Added files from Apple's ZipBrowser sample application.

Full ZipBrowser code is from
http://developer.apple.com/library/mac/#samplecode/ZipBrowser/Introduction/Intro.html#//apple_ref/doc/uid/DTS40007830
Fixed compiler errors and warnings in ZipBrowser source.

Removed references to unused ZipEntryView class.  Removed unneeded
-windowControllerDidLoadNib: method that referenced ZipEntryView.

Fixed ARC error related to NSError out parameter.

Added casts to silence trivial integer truncation warnings related to 64-bit code.
Implemented decompression of downloaded Auto-Ingest tool.

Added DataBuffer class that extends ZipBrowser FileBuffer class and provides
ZipDocument with zip archive data from memory rather than from disk.

Added -setFileBuffer: method to ZipDocument so that a DataBuffer instance can
be set on the ZipDocument directly.  Also added -rootEntry getter method to
expose the root ZipEntry object.

Modified -readEntriesForOperation: and -readFromURL:ofType:encoding:error:
methods to read from the zip archive synchronously rather than using
NSOperation and -performSelectorOnMainThread: calls.

Expanded -connectionDidFinishLoading: method in AutoingestionTool class to
find and decompress the Auto-Ingest tool from the downloaded zip archive.
Added a property for the download URL and split the kAutoingestionPath
constant into separate constants for the directory and filename.
Write Auto-Ingest tool out to disk after extracting it.

Extended -connectionDidFinishLoading: method in AutoingestionTool class to
create a temp folder at /tmp/com.ablepear.autoindigestion.installer and
extract Autoingestion.class there from the downloaded zip archive.

Modified the postinstall script to copy the Autoingestion.class file to
/Library/Autoindigestion and remove the temp folder.  Also changed postinstall
to put the Vendors folder and ExampleVendor.plist file in the admin group
and make them group writable.

Removed commented out code in ZipDocument.m and fixed typo in the preinstall
script.