Improve the formatting for the user page bio

Resolves #13406 (closed).

Problems, per the Issue above:

• The bio has an extra period appended by the HAML view.
• The bio isn't given its own line, not differentiated from username and account creation date.
• The bio is allowed to span almost the full width of the container, would probably look better if it were only allowed a max width of something like 750px.

This commit:

• Separates the User page bio from the username and account creation date.
• Separates the pseudo-selector adding a Middle Dot out from the profile-link-holder class and into a middle-dot-divider class.

Before:

With this Merge Request: