Improve the formatting for the user page bio

Resolves #13406.

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:
![Screen_Shot_2016-02-15_at_3.55.28_PM](/uploads/fbe410c3f436740121c5f4686e0f44d0/Screen_Shot_2016-02-15_at_3.55.28_PM.png)

With this Merge Request:
![Screen_Shot_2016-02-15_at_3.55.25_PM](/uploads/b4b16376a395608f57d8f76ab47e241f/Screen_Shot_2016-02-15_at_3.55.25_PM.png)

See merge request !2827