Cleaning up

- Renaming secret -> private
- Fixing a poorly named method
Merge branch 'master' of github.com:Tabbedout/SodiumObjc
Adds nonce packing/unpacking to public-key encryption methods
Adding nonce packing to private-key encryption methods
Moving nonce to the head of the data buffer (instead of the tail)
Adding additional unit tests
Adding a test to ensure the seed is at the head of the private signing key
Merge pull request #6 from damiancarrillo/packed-nonce

Adds nonce packing/unpacking methods
Copying public header files to Derived Data directory
Merge branch 'master' of github.com:Tabbedout/SodiumObjc
Using system-style header imports
Copying additional headers to the derived data directory
Make the NACLSigningPublicKey return the length of a signature
Merge pull request #7 from Tabbedout/signature_bytes

Make the NACLSigningPublicKey return the length of a signature
added Ilter's Podspec
make podspec point to original repo
updated sodium.h (thanks Ilter)