Fix typo in comment of jquery-bootstrap example
Improve comment in example code

This should make it more clear that even though `$` is used in 4 methods, only 2 of them are crucial for integrating the modal into the components lifecycle methods and the other 2 are just helpers.
Add placeholders for static prop type tests

This is where tests of static prop types should go when we have the
infrastructure set up to handle it.
Merge pull request #2586 from RileyTomasek/master

Fix typo in comment of jquery-bootstrap example
Merge pull request #2745 from sebmarkbage/types

Add placeholders for static prop type tests
Separate createElement and JSX tests

This essentially copies all classic element creation tests to the modern
JSX tests. The classic tests doesn't use JSX and modern tests do.

The idea is that the JSX tests can start dropping dynamic checks once
we have Flow support for those features. JSX won't be necessary for
dropping dynamic checks. Plain object will also work. Flow will also not
be necessary for JSX. However, the tests should test for the suggested
combination (JSX + Flow).

This also moves some misplaced tests to ReactDOM and Validator.

Note that the modern tests uses ES6 classes. I will add separate tests for
those. However, these are not guaranteed to have .displayName so all our
error messages should check .name if available instead. This should be
better abstracted but I just adhoc fix this for now.