Added GeneralPurposePacker.

Lower level interface to the C msgpacker than the MessagePackPacker class. Allows the user to write NSString and NSData objects into the packer, before flushing it into NSData output.
Updated podspec for version 1.2.0.
GeneralPurposePacker packing numbers and objects.

Copied the implemenation from the MessagePackPacker. Next step: make the MessagePackPacker use the GeneralPurposePacker.
Updated podspec to version 1.2.1.
Created GeneralPurposeUnpacker.

Unpacks a message by reading off the parts one by one.
Updated podspec for release 1.2.2.
Added support for unpacking raw NSData objects.
Fixed code style in GeneralPurposePacker.

K&R style braces.
Added typed reading in GeneralPurposeParser.

New methods that read NSNumber, NSString or NSData, or return nil.
Put documentation in GeneralPurposePacker.h.

Moved it from the .m file. Is this how it is supposed to be? Objective-C is WEIRD.
Updated podspec for release 1.2.3.

Such pretty version code! <3