enketo_url helper function to support edit urls
edit_data view, use new enketo api
should use /api_v1/instance for ENKETO_API_INSTANCE_PATH
test enketo remote server response, remove irrelevant test
use enketo test server_url incase we are testing
use RequestFactory for test
use https for ENKETO_URL
Merge branch 'master' into enketo-edit-api

Conflicts:
	main/tests/test_form_enter_data.py
upgrade requests module from 0.14 to 1.2.3
handle exceptions properly: enketo_url should within the try...except block
mock the test to enketo with httmock module
Merge pull request #1217 from modilabs/enketo-edit-api

use enketo edit api