Produce main bundle with Rollup

[gaearon]

There are unfortunate Babel artifacts in the compiled UMD bundle.
For example:

return e&&e.__esModule?e:{"default":e}}t.__esModule=!0

// Oops, we access ["default"] in a hot path!
if(!(0,u["default"])(e))throw Error("Actions must be plain objects. Use custom middleware for async actions.")

We should use a better build process that doesn’t produce artifacts like this.

[timdorr]

This is due to the oldIE support stuff, right? Shouldn't be happening in next branch. Scope hoisting (aka, rollup) won't fix this by itself.

[gaearon]

I meant the Babel default indirection which goes away if we compile with Rollup.

[TrySound]

@gaearon Do you want a PR?

[gaearon]

Sure.

[TrySound]

@gaearon Done