Refactored reading of Glottolog data
Refactored reading of Glottolog data

It turns out that reading large CSVs turning each row into a `namedtuple`
is orders of magnitude more expensive than reading `dict`s. Refactoring
`load_glottolog_data` accordingly (and recycling objects from the first
pass for the second) cuts down the test run time to about a third.

lmaurits/BEASTling