fix let! indentation in features/spec/user_profile_page
Validate username to only contain letters
User show page url displays as users/<username>
Add to_param method to user model
Merge branch 'master' of https://github.com/elizabrock/squmblr

Conflicts:
	app/models/user.rb
	spec/features/user_profile_page_spec.rb
Merge branch 'master' of github.com:mknicos/squmblr into mknicos-master

* 'master' of github.com:mknicos/squmblr:
  Add to_param method to user model
  User show page url displays as users/<username>
  Validate username to only contain letters
  fix let! indentation in features/spec/user_profile_page
Merge branch 'mknicos-master'

* mknicos-master:
  Add to_param method to user model
  User show page url displays as users/<username>
  Validate username to only contain letters
  fix let! indentation in features/spec/user_profile_page
Convert all manual User creation in specs to use Fabricate.