CCFile

Initial implementation of the CCFile class. The basic functionality and tests were done so quickly that I decided to go ahead and implement gzipped and encrypted streams.

For encryption, I went with the XXTEA algorithm since it was really easy to use. It's not going to be foolproof anyway, so I didn't see much point spending more than a couple hours on it. I made a little command line utility to perform the encryption as well. It's pretty basic. It encrypts 4kb blocks of data at a time, where the first four bytes of each block are the total number of bytes in the block. Files will be rounded up to the next 4kb in size. ~~Right now the key I used for the tests is hardcoded. I figured eventually we'd probably add a SpriteBuilder setting to generate a key for a project and have the user copy paste it into their app delegate. Sort of like TexturePacker did `[CCFile setEncryptionKey:@"0123456789ABCDEF"];`~~ (This method has now been added.)
`loadPlist` calls the `openInputStream` method, but it doesn't call `loadData`. The reason why I took shortcuts with that test was because Xcode may or may not reencode the XML pilst file as a binary plist file. It seems unlikely that the `loadData` method would have anything wrong with it as long as it returns something.