Add support to JSX transform for <hyphenated-tags>

This only adds support for whitelisted tags, not arbitrary ones.

Closes #1539
Support more properties for image maps

Supporting the `<area>` tag is pretty useless if we don't support the necessary properties.
add count() method to ReactChildren

added ReactChildren.count() to count the number of children, and a test case.
Cleanup ReactChildren
Remove jest usage in ReactDescriptorTest

Until we're only using jest on github, we should stick with Jasmine spies. Soon, hopefully.