Fix bug in balanced path

Fixed a bug with precedence when the comparison function is not
enclosed in parentheses
Add support for comparator in merge
Merge pull request #322 from roshanr95/merge

Merge
Refactor dispatch_sort() function
Add extents<N> class

This adds an extents<N> class which stores an array of n-dimensional
extent values. This can be used to represent an ND-range for launching
an OpenCL kernel or for storing the size/shape of a 2D/3D image.

Also adds a variadic dim() function which provides a concise syntax
for creating extents<N> objects.
Fully qualify call to bind() in nth_element()
Merge pull request #323 from kylelutz/extents

Add extents<N> class
Merge pull request #324 from kylelutz/refactor-dispatch-sort

Refactor dispatch_sort() function
Merge pull request #329 from kylelutz/fully-qualify-bind

Fully qualify call to bind() in nth_element()
Add cl_gl_ext.hpp forwarding header
Merge pull request #332 from kylelutz/cl-gl-ext-header

Add cl_gl_ext.hpp forwarding header
Add utility directory

This adds a new utility directory and moves some of the utility
functions and classes (e.g. dim(), extents, wait_list) there.
Add test for flat_map with custom kernel
Merge pull request #334 from kylelutz/utility

Add utility directory
Merge pull request #335 from kylelutz/flat-map-custom-kernel

Add test for flat_map with custom kernel
added histogram example based on opencv
Merge pull request #330 from Mageswaran1989/histogram_example

added histogram example based on opencv
max_element perf added
Merge pull request #337 from skozilla/master

max_element perf
Add result_of<F(Args...)> meta-function