Add hasOwnProperty checks where appropriate

For boolean-like objects, I've added hasOwnProperty checks in addition to the existing truthiness check even though for most of these dicts, we leave out false keys instead of setting them explicitly to false.

In DOMPropertyOperations, we don't need to check hasOwnProperty if the property is in isStandardName because (with the exception of getPossibleStandardName) the dicts on DOMProperty will now be consistently populated with every valid attribute.
Update Jasmine link
Merge pull request #1552 from t3chnoboy/master

Update Jasmine link
Fixed spacing of invalid checksum warning
Tweak getting started wording
Be more specific with createClass, renderComponent

Closes #371.
Mention PropTypes in top-level API

cf. #449
Asynchronously load scripts with JSX transformer.
Merge pull request #1558 from nhunzaker/fix-1530

Fix 1530 - Asynchronously load scripts with JSX transformer
Allow unmounting title tag

cf. #1376.

This is useful for SVG. Dynamically adding and removing `<title>` elements in SVG still won't work properly because of getMarkupWrap but this at least lets you include it in initial render and then unmount the entire `<svg>` without problems.
Merge pull request #1189 from spicyj/hasown

Add hasOwnProperty checks where appropriate
Use Object.prototype.hasOwnProperty for doc in IE8

Test Plan: Loaded ballmer-peak example in IE8 without errors and interacted with the text field.
Merge pull request #1564 from spicyj/hop-ie8

Use Object.prototype.hasOwnProperty for doc in IE8
Don't fail Travis on sauce failures

Fixes #1496.
Merge pull request #1563 from spicyj/travis-no-sauce

Don't fail Travis on sauce failures
Switch style test to pass in jsdom

This should be testing approximately the same thing and passes in Jest.

Test Plan: Cherry-pick Jest config from #1528 and verify that running `jest`.
Add configuration for running tests with Jest

Can be run with `node_modules/.bin/jest` for now; didn't want to disturb the grunt setup.

Right now one test fails with:

```
 FAIL  browser/ui/__tests__/ReactDOMComponent-test.js (1.423s)
● ReactDOMComponent › updateDOM › it should update styles when mutating style object
  - Expected: '0' toEqual: '0.5'
        at Spec.<anonymous> (src/browser/ui/__tests__/ReactDOMComponent-test.js:99:33)
```

which I can only assume is a jsdom problem -- no other asserts fail.
Merge pull request #1571 from spicyj/style-test

Switch style test to pass in jsdom
Merge pull request #1553 from givingstage/invalid_checksum_warning_spacing

Fixed spacing of invalid checksum warning
Merge pull request #1559 from spicyj/gh-1376

Allow unmounting title tag