Version 2.2.0 released

The new version comes with lots of enhancements. Highlights are

• Support for NIFTI-1 image files
• Basic support for HDF5 image files
• Support VTK >= 6 data IO
• Cost functions with mask support in voxel based image registration
• Filter chains can now contain combiners, load and store intermediate results.
• 3D orientations are better tracked
• More C++11