Add algorithm and test for set_union
Add algorithm and test for set_difference
Add algorithm and test for set_symmetric_difference
Add algorithm and test for includes
Merge pull request #115 from roshanr95/set_algorithms

Set algorithms
Simplify lambda wrappers for binary geometric functions
Add test for find_if() with distance()
Add image2d::clone() method
Add variadic wait_for_all() function
Move variadic event handling to async/wait.hpp
Merge pull request #36 from kylelutz/develop

Update Develop