Add python-nexus to dependencies
Add LangaugeTree model & Migration
Script to load language tree
Add language to SocietySerializer
api_view for LanguageTree objects
Add API to get trees from language Ids
Add name to LanguageTreeSerializer
add distinct() to LanguageTree query
TreesFromLanguages service

Annotates societies with language trees after search
Show language name and tree count on results
Add popover to list trees for a language
Merge branch 'master' into language-trees

Conflicts:
	dplace_app/static/js/controllers/search.js
	dplace_app/static/partials/societies.html
Update language tree search to use searchModelService
Merge pull request #104 from NESCent/language-trees

Basic support for language trees