Merge pull request #72 from rkskvk/develop

Added - gather, gather_if and Appropriate Google TestCases
Updated scatter/gather doc
BTBB Folder contents are now copied to the package.
 Implemented the TBB functions for copy, copy_n, fill, fill_n , generate, generate_n, min_element, max_element, inner_product, stable_sort, stable_sort_by_key and sort_by_key

 Added Partial Checked_Iterator support for Inner_Product

 Enclosed Large Buffer test cases within preprocessor statements

 Added a few more test cases for offset & for different data types to verify the correctness of the newly implemented TBB functions.
Added btbb files for copying them to the package.
Removed the thread header file from scatter.inl and gather.inl and removed some redundant code from reducebykey.inl