Remove attr_accessible from the user model

* Move to strong parameters
Use `breadcrumbs.tap do |links|` to silence a deprecation warning

- Found when running the Cucumber features.
Rearrange a Cucumber step definition

- This enables one failing feature to pass as the specific feature
  needed to "see" the dropdown of the tags as it typed, not click a
  button after filling in the tags filter. Thanks jennyd.
history_spec tweaks

* Re-add the specific class of expected error when user is not set
  (deprecation of supplied type only applies to `.not_to raise_error`)
* Tweak the language (drop 'should', let the context do the work of
  explaining)