blurBehavior change default to 'add' not 'clear'

[bnbon]

I feel this would make more sense than clearing it when the focus changes... when entering a single value, people do not instinctively press return/space/comma, they just click the next field.

This is also based on a round of UI testing done internally, and the "add" value made a huge difference.

Just a suggestion.

[leMaik]

Good point. 🤔 This would be a breaking change, though, but I see why this would be good.

[leMaik]

Since this is a breaking change, it's not going to happen in v1 (i.e. the Material-UI v1+v3 version). But in v2.0.0-beta.2, this is changed, so it will default to add in the Material-UI v4 version.