Tab overflow menu triggers unnecessarily

[sdaitzman]

Feedback summary

Tabs component triggers overflow to a "More..." menu when there's enough space to display the remaining items. The first example is from the new Content Libraries staging server, and the second is from EdX Studio. I can't replicate this issue on the Paragon documentation site.

Improvements

• Potential API improvement: add an option to disable the overflow menu

Bugs

• Bug fix: only resort to overflow menu when there isn't enough space

CC @bradenmacdonald @lizc577