Add link to the createClass spec in the lifecycle docs

[chrismendis]

It's surprisingly difficult to glean the exact specification of createClass from the React docs. This presents some difficulties with figuring out what exactly one can do with the lifecycle function.

Perhaps we can at least add a link to the actual spec in the React code? This is admittedly a bit fragile, but I can't think of a better solution off the top of my head.

[istarkov]

Hi thank you,

The link you've added is not stable, any change to ReactClass.js could make this link broken.

I agree that current React documentation make it difficult to understand what is specification object without links to https://facebook.github.io/react/docs/react-without-es6.html etc.

BTW I think in the future createClass will be deprecated, so giving a link to specification object with all that mixins property can be bad idea ;-)

For now I think that lifecycle enhancer is also bad idea ;-), I almost removed it from my code. As in all places I used it, it was better to use usual es6 class for component itself.

[chrismendis]

@istarkov sounds good! I also had to abandon using lifecycle because I needed to use refs.