1) Implemented std::valarray serialization (based on vector.hpp) in file valarray.hpp
2) Implemented unit tests in file valarray.cpp (based on vector.cpp tests, except for bool case)
3) vs2013/unittests project configuration updated accordingly
4) unittests/common.hpp updated.
5) No documentation so far
If someone attempts to have both a versioned and non-versioned serialization
function, they will get a compile time error.
relates to improvements in #23
