fix median scaling

[arlin]

History. As per phylotastic/datelife#57 we were getting unexpected results including changes in topology. The reason is that the portal has been getting a scaled tree using the names in the input tree while discarding the input topology. We want to preserve the input topology.

• determine how to invoke the DateLife median method so that it preserves the input topology
• if the portal is using an intermediate phylotastic service that needs to be rewritten, do that
• fix the portal so that it is invoking the service in a way that preserves the input topology.

[arlin]

@bomeara I'm assigning this to you first so that you can address the first issue above, how to invoke DateLife. Then we will re-assign this to @abusalehmdtayeen and @ducvan0212