Added TcpConnection tests.
Merged test_tcp_client.{c,h} and test_tcp_server.{c,h} into test_utils.{c,h}.
Tests code clean-ups.
Moved the ENABLE_TESTS option in the CMakeLists.txt in the root of the project.
Conditionally enable testing.
Merge branch 'develop' of https://github.com/rugginoso/rapp into config