Only unmount ReactEditorView's component before removing if its mounted

Fixes #3108

Unmounting the component the first time can cause a focusout event,
which leads to a redundant removal and an attempt to unmount again. This
protects against that.
Upgrade to React 0.11.1
Upgrade to pathwatcher 2.0.6
Upgrade to runas 1.0.1
Upgrade to apm 0.86
Require the react-editor-view where we require the editor-view
Fix the mini-editor test
Remove the editor-view
Merge the react and non-react editor styles
Upgrade markdown-preview: no more EditorView dependency
Only focus when the component is mounted
Add `will-insert-text` and `did-insert-text` to `insertText()`
::getModel() returns the editor
Sometimes there might not be a selection.