Fixed toolbar: text jumps on selection

[ksuess]

Steps to reporduce

• Fix the Slate toolbar (config.settings.slate.showExpandedToolbar = true;)
• select text
• deselect text by setting cursor somewhere else

Expected behavior
Toolbar is always visible while block is active.
That means toolbar does not vanish on deselecting text.

[tiberiuichim]

@ksuess I've restructured the toolbar, we're getting rid of the "expanded" mode, right now we'll only have the floating toolbar.

On the other hand, the toolbar is a lot better responsive and there's been many improvements to normalization of blocks. Watch the next release, it will be great.