added test for 2-dimensional kd-tree
changed NULL to nullptr to avoid ambiguous coding
changed termination conditions and add option for assigning step
updated README.md, TODO.md, documentations
fixed a bug in seeding method for kmeans++
changed the name of assign methods
make the assignment part more focused
changed the implementation from by clusters to by labels
updated the doc
fixed log at test_kmeans program and added OpenCV's version checking
implemented Greg's method for linear assignment
updated the doc
covered the updating bounds action
fixed bugs
made changes:
* floating-point type was changed from double to float
* Implemented Greg's method
Merge pull request #7 from marker68/v1.0

V1.0