Add in RandomNonceBox implementation

This class implements a strategy for nonce generation and transport,
that of randomly generating 24 bytes and then prepending them to the
ciphertext.  To decrypt, the reverse operation is called.
Make docs/constants consistent for RandomNonceBox

This is mostly making sure we use same named constant, etc.
Add specs for the RandomNonceBox

Which did actually catch a very important error: The box method was
returning the plain text (!).  Otherwise, they mostly check things like
round tripping.
Try and solve the encoding errors on rbx-19

Make sure we have 8-bit zeros.
Merge pull request #24 from cryptosphere/random_nonce_box

Add in RandomNonceBox implementation
Dragons belong at the edges of the map

Moving the Scalar documentation down to the bottom of the README.
Documentation on Hashes and Authenticators is likely to be more
interesting to a lot of users of the library.
Document the Hash module

The library is now about 80% documented, according to YARD's stats.
Mostly its the NaCl constants pulling it down.
Document CryptoError
Mark NaCl module as private

Really, it's just for hanging constants and method bindings off.