Make Y.Array.indexOf()'s fromIndex param fully ES5-compatible.

Added fromIndex argument to Array.indexOf() method.

Support sparse arrays correctly in the non-native Y.Array.indexOf() and Y.Array.lastIndexOf(). [Fixes #2530966]

Handle sparse arrays correctly in array methods. [Fixes #2530376] The non-native implementations of the following methods were modified to handle sparse arrays correctly: - Y.Array.each - Y.Array.every - Y.Array.filter - Y.Array.find - Y.Array.hash - Y.Array.map - Y.Array.reduce - Y.Array.some

Add Y.Array.dedupe(). This method provides a fast deduping implementation for arrays that contain only strings. To dedupe an array that may contain values that aren't strings, use Y.Array.unique().

Move Y.Array.forEach alias to yui-array.js where it belongs.

Refactor Y.Array unit tests and add a bunch of missing tests.