react 15.2.1

Fix errant warning about missing React element. (@gaearon in #7193)
Better removal of dev-only code, leading to a small reduction in the minified production bundle size. (@gaearon in #7188, #7189)

Add stack trace to null input value warning. (@jimfb in #7040)
Fix webcomponents example. (@jalexanderfox in #7057)
Fix unstable_renderSubtreeIntoContainer so that context properly updates when linked to state. (@gaearon in #7125)
Improve invariant wording for void elements. (@starkch in #7066)
Ensure no errors are thrown due to event handlers in server rendering. (@rricard in #7127)
Fix regression resulting in value-less submit and reset inputs removing the browser-default text. (@zpao in #7197)
Fix regression resulting in empty name attribute being added to inputs when not provided. (@okonet in #7199)
Fix issue with nested server rendering. (@Aweary in #7033)

Make ReactPerf.start() work properly during lifecycle methods. (@gaearon in #7208).

Fix issue resulting in spurious unknown property warnings. (@batusai513 in #7165)

Improve error handling in cross-platform touch event handling. (@yungsters in #7143)