support multiple tours with some not run

[jjb]

before this, if a tour was encountered where tourMayStart
was false, then subsequent tours were not attempted

now, all incomplete tours are looped through until the first
runable one is run

for...in is used because it is the most compatible

example tour that this fix accommodates:

non_admin_intro:
  steps:
    1:
      text: "Welcome User!"
      attachTo:
        element: "#non-admin-tour"

admin_intro:
  steps:
    1:
      text: "Welcome Admin!"
      attachTo:
        element: "#admin-tour"