ReactJS support for IE6/IE7

Following changes were made to support old IE browsers IE6 and IE7
1. Algorithm to distinguish user event value changes and JS value changes on INPUT and TEXTAREA in ChangeEventPlugin was reimplemented by using data-ie8_value attribute on DOMNode
2. String[0] replaced by String.charAt(0) in setInnerHTML
3. Added querySelectorAll polyfill
4. Checking renderNode.hasAttribute extended by IE7 compatible attribute check
To run react.js apps in IE6/IE7 you have to use es5-shims and console-polyfill