v0.2.0

• Fix refinement of optional nullable types
• Typecast expressions (warning - not added to strip out transform yet)
• treat throw as similar to return
• Switch from React to react (React still included until facebook/react#3031)
• Fix types for sessionStorage and Storage
• tighter type for undefined values
• no lib paths fix
• Fix exporting types for builtin modules
• Add Number.isNaN and Number.isSafeInteger type annotations
• Optional properties in objects & optional type revamp