Include Jaeger's distance function

[PhyloStar]

Implement the doculect distance function for Jaeger (2013) paper:
"Phylogenetic Inference from Word Lists Using Weighted Alignment with Empirically Determined Weights"

[Anaphory]

Calculating Jäger's dER sounds like a different beast to me than clustering cognates using various methods. It might go into a different package from the cognate alignment and clustering methods, though, and one strong connection is that the distance function d he uses does not need to be ASJP-based edit distance, but can also be our edit distance using PMI scores.