Update Observer component definition

[RafalFilipek]

Hi!

Right now we have to wrap observerd value with HTML tag like:

const C => <Observer>{() => <div>{obser.vable}</div>}</Observer>

With this change you can just return observed value

const C => <Observer>{() => obser.vable}</Observer>

Thank you!

[mweststrate]

Great, thanks!

[danielkcz]

@mweststrate Do you plan to release a new version soon? This one is particularly annoying since I cannot return null from there.

[mweststrate]

@FredyC yeah, I want to release if #403 is in. If that is not today, I'll probably cut a release at the end of the day anyway