Test Flexbox support

[chris-muller]

Test flexbox changes to ensure they:

• Have not affected existing features.
• Correctly work in all expected situations.
• Work correctly when flexbox and floatbox are used together.

[smiLLe]

https://github.com/philipwalton/flexbugs#8-flex-basis-doesnt-support-calc

Hi,

i've seen that you are using flex-basis with calc. I have implemented a similar library for internal company usage but the more we were using column layouts with flex-basis the more problems we had in IE 10 + 11.
In the end, we now use
width: calc(..code..);
flex-basis: auto;
flex-grow: 0;
flex-shrink: 0;

In almost any cases where you could use float layouts, this will work with flexbox, except you can use align-items order justify-content.