Don't escape slash; it's unnecessary

Fixes #1444.

Test Plan: grunt fasttest
Fix to sample code for href in ReactPropTypes

Error should be thrown in the previous condition is "not" meet. And the href propType is described as optional in the comment, but the null check was missing.
Wrapped line to 80 chars in ReactPropTypes sample
Add --harmony option to live JSX compiler page
Merge pull request #1760 from spicyj/docs-harmony

Add --harmony option to live JSX compiler page
[Docs] Put tutorial up-to-date with the code
Merge pull request #1763 from chenglou/docs-tut

[Docs] Put tutorial up-to-date with the code
[Docs] Fix tutorial line highlights, revert ajax in cb
Merge pull request #1765 from chenglou/docs-tut-again

[Docs] Fix tutorial line highlights, revert ajax in cb
fix link in community roundup #18
Merge pull request #1767 from jgebhardt/fixlink

fix link in community roundup #18
Cache node_modules on Travis

This isn't actually enabled yet for public projects, but this will help
us speed up builds when it does get enabled.

http://docs.travis-ci.com/user/caching/
Merge pull request #1750 from protron/patch-1

Fix to sample code for href in ReactPropTypes
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.
Stop running so many things in travis

We're not actively looking at most of these and they take up valuable
job time.
Give context for owners of compenent instantiations with propType errors

See modification to the test-file: Basically we add a small hint at the end
of the error warning for propType errors to help identify which instantiation
of the component at hand is faulty.