Improved linker module. 

This fork contains an improved linker module. The improved linker module consists of 5 major changes.
1. No longer uses temporary array, final_mask, in the linker.pyx script. 2. Fixed the initial bug that was limiting the linker module to 10,000 sources. 3. The linker module now uses the latest version of the RJJ_ObjGen library. 4. Updated the custom RJJ_ObjGen library to the latest version of the publicly available RJJ_ObjGen library. I didn't use an exact copy of the latest version, because the move constructors and move operator are strictly C++11 features that aren't supported by all compiler, and aren't necessary here. 5. The merging lengths are now the distances (in voxels/pixels) between voxels/pixels that will be linked. They are no longer the number of empty voxels/pixels separating voxels/pixels that will be linked.