Style popups

[mietcls]

The popup for adding a handle can use some love:

• It’s not centered on the page
• The black overlay is not covering the left most panel
• It’s not styled yet

[ismakutl]

Fixed styling + issue #116. Didn't style facebook, because we are not going to use that.
I will close this issue after it's reviewed.

[mietcls]

@ismakutl what branch is this?

[ismakutl]

@mietcls I did both in issue/branch #114.

[mietcls]

@ismakutl A list of issues regarding to the popup: #120, #122, #123, #124, #125

[ismakutl]

Can I work on this branch? Or should I make seperate branches for each issue?

[mietcls]

Sure, work on this one, I should've maybe commented it here — sorry bout that!

[ismakutl]

Solved these issues (#120, #122, #123) in the branch #114