Export Atom's version of React and Reactionary

Fixes #3101 and works around facebook/react#1939.
Absolutify the placeholder text in mini editors.

Fixes #3118
Style the mini editors for a constant height

Adds an @input-font-size variable.
Upgrade atom-light-ui for mini editor fixes
Upgrade settings-view for mini editor changes
Upgrade dark-ui theme for new variable
Pull the mini editor styles out from react rule
Merge pull request #3121 from atom/bo-style-mini

Style mini editors
Merge pull request #3102 from dmnd/export-atom-react

Export Atom's version of React and Reactionary
Un-f
Upgrade to git-utils 2.1.3
Upgrade to nslog@1.0.1
Upgrade to oniguruma 3.0.2
Upgrade to spell-check@0.40
Upgrade to oniguruma 3.0.3
Upgrade to pathwatcher 2.0.5
Upgrade to scrollbar-style 1.0.1
Upgrade to symbols-view@0.63
Upgrade to apm 0.85
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.