input[type=date] in .form-group has resizing oddity on very small viewports

Created by: cvrebert

Example: http://jsbin.com/uLiSOfUt/2 Browser: Chrome Resize the viewport to <280px and observe that the date input stops getting narrower and remains at a minimum size (causing the right portion of it to go offscreen), while this doesn't happen with the text input. If you get rid of the .input-group and just put the date input directly within the .form-group, the problem does not occur.