Fix SEGV on 32-bit architectures

Fixes #1

Previously lengths were passed to functions as `int` but the function prototype requires `long long`.  64-bit ruby was fine with this, but 32 bit barfed.
Attach and wrap with one function call

Saves typing out the crazy long NaCl function names twice, saves typing
the unneeded :int at the end of the definition, and also now with bonus
documentation
rewrite hash to use the newly wrapped function

Also, document the hash method.
Merge pull request #2 from namelessjon/bugfix/segv

Fix SEGV on 32-bit architectures
Defunct
Allow rbx failures as Travis+FFI+rbx don't get along atm
Merge pull request #3 from namelessjon/dev/fixwrap

Refactor wrapping method
Pull in the sodium-randombytes library
Revert "Pull in the sodium-randombytes library"

This reverts commit 610c0101a7abb249e95cfd5e4b9be0f658130ca6.