Menu container positioning

[aldhsu]

Related to #298 #318 .

Expected

• Specifying menuContainer to an element that has relative positioning will position the menu correctly inside the container

Actual

• container is positioned incorrectly unless it is vertically the lowest element on the page
  

See https://codepen.io/aldhsu/pen/WNeWMxm

[mrsweaters]

@aldhsu This looks good and thank you for updating the test suite! I'll merge this in.

[pleunv]

This change seems to have completely broken positioning for us in cases where there's not enough space on the bottom and the menu instead positions on top of the trigger. By default we don't specify a menuContainer and instead render in the body, I've tried specifying a custom menuContainer which makes the positioning even worse (the container is relatively positioned). Will see if I can make a repro, but for now we're forced to pin to 3.x.

Edit: Correction, apologies. We had a menuContainer before as it was necessary to fix the positioning. After 4.0 specifying the menuContainer now has the same effect as specifying no menuContainer, resulting in the positioning being completely off. I'm not sure if I'm missing something here.

Strangely enough removing menuContainer and putting position: relative on the body seems to work, but that's not really something I want to do.

[loicndjoyi]

@pleunv did you find a different solution than putting position relative to the body?