Rewrite popup tail direction calculation
Position tail along the popup side so that it points to the center of the target element
Merge pull request #311 from yandex-ui/calculate-popup-tail-direction

Исправить вычисление направления хвостика
Checkbox styl refactoring
dropzone-refactoring
gap-refactoring
Icon refactoring, fix #273
input refactoring
Popup and some smaller blocks refactoring
Select and other refactoring
slider
suggest
tabs
toggle
toggle
user
fix after review
fix after review
fix after review
fix after review