v6.0.0-alpha.9

• Now treats null the same as undefined when defaulting to defaultValue or ''. Reported by @gederer on #703.
• Added ES build to allow tree-shaking 🌴 🌳 🌲 Thanks to @xdissent for PR #937.
• Shallow equal on Field and FieldArray shouldComponentUpdate. PR #940 from @leesiongchan. Fixes #936, #931.
• Made smarter hasErrors logic. Fixes #943.
• Keep track of submit promise to fix multiple submit and async validation requests. #829 #888