Remove MurmurHash from Beast and RippleD

The only use of MurmurHash in RippleD is to hash a public key to generate a hostid that is displayed to non-admin users in lieu of the actual system hostname. This pull replaces that with the classic [Jenkins](http://en.wikipedia.org/wiki/Jenkins_hash_function#one-at-a-time) hash, and removes MurmurHash from Beast.

Reviews: @ximinez, @josh-ripple, @vinniefalco
fnv1a, SipHash and SpookyHash are sitting in hash_append.h. Does it make sense to reuse one of them?