Merge updated remote library
Fixed cast to local Tree object from remote Tree object
Merge branch 'dev-taxondiff', remote branch 'origin'
BUG: On attempting to copy a subclassed dendropy tree using copy.deepcopy:

/nfs/research2/goldman/kevin/local/lib/python2.7/site-packages/dendropy/dataobject/base.pyc in __deepcopy__(self, memo)
    257             o = self.__class__(target=memo[id(self.target)])
    258         except KeyError:
--> 259             raise KeyError("deepcopy error: object id %d not found: %s" % (id(self.target), repr(self.target)))
    260         memo[id(self)] = o
    261         for a in self:

KeyError: 'deepcopy error: object id 48413264 not found: Tree
Bug fixed / avoided by changing TrClTree.cast method - could do away with casting entirely by using dendropy's in-built .clone_from method
Added instructions to README
Disabled kmedoids clustering when Biopython is not installed
disabled evrot for now
Merge branch 'master', remote branch 'origin' into dev-taxondiff
Fixes to DistanceMatrix, TrClTree, to problems arising from new Tree / TrClTree objects