Provide alternative keys
Merge pull request #7 from erwan/alt2

Provide alternative keys
v1.4.1
#8 Generate a function value
#10 Support empty messages
v1.4.2
Fix README
Fix for subset in Java keys where not passed
Merge pull request #12 from tuxBurner/master

Subset was not working in Java
Make the API more extensible
v1.5.0