Added common website password hashing functions

```clojure
luminus.hashing=> (luminus.hashing/md5 "abc")
"900150983cd24fb0d6963f7d28e17f72"
luminus.hashing=> (luminus.hashing/sha1 "abc")
"a9993e364706816aba3e25717850c26c9cd0d89d"
luminus.hashing=> (luminus.hashing/sha2 "abc")
"ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad"
luminus.hashing=> (luminus.hashing/sha2 "abc" "salty")
"da3a54b1d94374ac909dcb5f34874a9f86b167040511023de41342e6f6e1222c"
```