Added symmetric authentication to simlify hmac
Added functions to generate and verify authentication tags for the given gadget
Changed Auth to Sign in RSA
Fixed raaz-cipher according to changed definition of Key type family
Fixed raaz-random according to changed definition of Key
Added CryptoInverse
Split primitives into symmetric and asymmetric
Fixed raaz-core
Fixed raaz-cipher salsa20
Fixed raaz-cipher AES
Fixed raaz-cipher tests
Fixed raaz-cipher benchmarks
Fixed raaz-random
Fixed raaz-modular
AuthMode changed to SignMode
Added Storable to Cxt of hashes
Merge some design change to simplify primitives

- We now have the notion of symmetric and asymmetric primitives