Add horizontal scrollbar to Unstaged and Staged views then stop eliding content

[laicasaane]

As in the screenshot below, this Unstaged view is at its max-width and I cannot expand it further to the right. I don't know if this is a design choice or technical limitation, however, I propose adding a horizontal scrollbar to both Unstaged and Staged views. That will both allow the design of forcing a max-width and solve the issue of long content being elided.

[DanPristupov]

#140