Lock some dependencies and update the bundle as well
Fix some syntax
Fix an issue with Guard when not using bundle exec

When not using bundle exec, Guard fails to load some dependencies.
Make some clean up in the test suite

Make the step definitions a little bit cleaner and put them into
a specific file. Also rely on regular expressions to make some common
steps non-redundant (mainly for models). Finally, make some steps a
bit more "English" like "When I submit the form".