* add enzyme test helper with lingui provider
* add router context to enzyme test helper
* get 18n, router, & config contexts rendering together in enzyme helper
* add config context to enzyme helpers
* add network and dialog contexts to enzymeHelpers
* convert OrganizationForm tests to use new mountWithContexts helper
* default all context value keys to default unless provided
* document use of mountWithContexts()
* fix typo in CONTRIBUTING.md
* update Organizations to use mountWithContext
Keith Grant