Fixed two bugs in the library. One dealing with the ItemStack implementation not correctly writing out -1 if the nbt data is null. The other is that the writeMetadata method in utils/IOUtils incorrectly calculates the header using the object type twice and not using the object index at all.
Merge branch 'master' of https://github.com/Steveice10/mc-protocol-lib
Minor edits to fix incorrect writing of values to streams
Merged conflicts
Merge branch 'master' of https://github.com/Steveice10/mc-protocol-lib