We were having the following issues:
- the indicator would sometimes stay red even if the password that was
entered was long enough;
- the indicator had a middle yellow signal: what does that mean?
- the red/green backgrounds were not color-blind-friendly.
Add a password strength indicator to SIGN UP and PROFILE pages
Fixes#1647
Added a password strength indicator to the sign up page. You can see how it looks in the following screenshot. In the sign up page, it checks if the password contains the username and alerts the user about it. If the user still wants to proceed with creating his account, nothing will stop him. This is merely a message. The indicator changes the input background color based on the strength like this:

The password strength indicator can also be found in the profile edit page. It functions in almost the exact same way, with the exception that it doesn't check if the password contains the username.

There are tests included.
/cc @job
See merge request !1227
The require jquery.turbolinks should be before the require turbolinks.
https://github.com/rails/turbolinks => "Add the gem to your project, then add the following line to your JavaScript manifest file, after jquery.js but before turbolinks.js"