Context test tools (#168)

* 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

jest.config.js

@@ -9,6 +9,9 @@ module.exports = {
     '\\.(css|scss|less)$': '<rootDir>/__mocks__/styleMock.js'
   },
   setupFilesAfterEnv: ['<rootDir>/jest.setup.js'],
+  snapshotSerializers: [
+    "enzyme-to-json/serializer"
+  ],
   testMatch: [
     '<rootDir>/__tests__/**/*.test.{js,jsx}'
   ],