test(unit): Add nanomsg unit tests

This adds unit tests which drive the nanomsg portion of the
library. The unit test script also now merges coverage
reports so that common portions of the library do not need
to be tested by both nano and nng tests in order to show
accurate coverage information.

Change-Id: Id852d46272972f481d4f37d8a60681228b4bc0ff
Signed-off-by: E. Scott Daniels <daniels@research.att.com>