[UI/UX] Fix the footer

* Remove the 'Development' / 'Production' version string. It's not
  useful for users since it's always 'Production'. Developers should
  know which environment they are running in, and for the most part it
  doesn't make a difference in terms of functionality.
* Fix weird code to remove duplication of the footer, which led to the
  brokeness (eg. different footer depending on whether you had a flash
  notice or not).
* Use link_to helpers to simplify the code.