chore: prepare for Cerebral@0.35.x and Cerebral@next

[edgesoft]

• remove Cerebral-view-react Mixin in demo
• update to cerebral@next for demo
• linting everything
• update to cerebral-view-react@next
• update to cerebral-model-immutable
• changed structure of demo app to comply to new website docs
• changed all React components to new connect syntax
• removed React specific folder.
• update README
• update devtools to @next

  33 This pull will fix this issue

[edgesoft]

@Guria waiting for your LGTM

[Guria]

Now we also have models exposed as 'cerebral/models/mutable' and 'cerebral/models/immutable':

import Model from 'cerebral/models/mutable'
import Model from 'cerebral/models/immutable'
import {mutable as Model} from 'cerebral/models'

could you also split into 2 commits:

chore: prepare for cerebral@0.35.x

feat: remove components reference implementations

BREAKING CHANGE:
React components removed. Examine new demo implementation for reference.

[edgesoft]

@Guria Humm, I don't think it's a breaking change. It's just the demo.

[edgesoft]

@Guria Well you are right. If they used the react wrappers it's a breaking change.

[edgesoft]

@Guria is this ok?

[Guria]

Lgtm.

[Guria]

@edgesoft fixed

[edgesoft]

Thanks @Guria !