This commit adds two test files: comm_split verifies the MPI_Comm_split functionaliy implemented in mpp::comm::split, and asynchronous_with_probe demonstrates the use of fully asynchonous message passing without prior knowledge of message size through the use of mpp::endpoint::probe and status::count. Note also that the namespace has been changed from mpi:: to mpp:: to disambiguate it, though this was done in the initial commit. Some other small, aesthetic changes were made as well.