Add scatterv and gatherv collective operations
Make scatterv and gatherv into collectives.hpp
Add hyperlinks to scatterv and gatherv in the docs
Fix indentation in scatterv.hpp and gatherv.hpp
Add tests for scatterv and gatherv
Merge pull request #6 from juliohm/develop

Add scatterv and gatherv collective operations

Tested with clang-5.1 on Mavericks and gcc-4.8.2 on Linux.  I'll make some wordsmithing, column 80, and a couple of other small changes after the commit.  Thanks Julio, nice work.