closes#9134
- Added form_id, input_id, and button_id parameters to subscribe_form helper
- Added id parameter to input_email helper
- Added test coverage to input_email helper
- Added quotes to id attributes for consistency
- Added subscribe_form helper tests
- Updated express to v4 in helper tests
no issue
- change out should.equal for // jshint ignore:line
- ensure should is the first require in every test, and ALWAYS require
- make sinon the second require, and sandbox the last thing
- ALWAYS use sandbox, futureproofs tests against contributors who don't know it
- change require formatting
