More tests for MerkleIndex and friends. Stuff sorta works. Other stuff sorta doesn't...
Fixes for the arrangement of merkle sections. Test to ingrate MerkleIndex w/ a changing (real) HashRing. Fixes for various bugs.
 * changed base64 to a non-standard base64 that preserves lexicographical ordering
 * changed Hash() class to be base64 aware.
 * renamed SynchronizerIntegrationTest to the more specific name SynchronizerExchangeTest
 * MerkleRing's split() and cannibalize() were going in the wrong direction, they're now fixed.
 * MerkleRing::splitSection() now accounts for the case where we're inserting at the end of the ring.
 * because I changed the base64 encoding, all the integration tests will be broken for a bit...
Calls to merkleIndex::cannibalizeSection() need to be made before the ring changes. Also, some test fixes.