Boxer => Box

Also #unbox => #open.  And fixing some specs.
libsodium notes
libsodium notes
SecretKey => PrivateKey

This avoids confusion with SecretBox.  Though public and private don't
abbreviate quite so nicely.  Ah well, such is life.
Move the #box and #open specs to be shared.

Since they can be, as long as we use the right key for the secretbox...
Crypto::SecretBox - secret key crypto with NaCL

This implements bindings to the `crypto_secret_box` family of functions
in NaCl.  They offer authenticated secret, rather than shared, key
cryptography, using the same primitives (xSalsa and Poly1305) as the
public/private key crypto in Crypto::Box.
Merge pull request #6 from namelessjon/dev/secretbox

Crypto::SecretBox - secret key crypto with NaCL
Make libsodium link more obvious
Use the libsodium-0.1 release

This should be quicker (no need to run autotools) and also more stable (no changes to libsodium breaking the build).
Still build based on libsodium dir

Less things to change when we increment the number this way!
Merge pull request #7 from namelessjon/libsodium-0.1

Use the libsodium-0.1 release