Test implementation with unique_ptr in inet_stream_server
Fixed memory leaks in unixdgram (unique_ptr)
Made inet_dgram exceptionsafe
Made stream_client_socket safe against exception-caused memory leaks
Merge branch 'issue-7'

issue-7 fixed memory leaks which could appear when an exception occurred
between allocation and planned deletion of larger strings in some
functions.
This issue was solved using C++11's std::unique_ptr which deallocate
their target at destruction time. Another possibility would have been
inserting delete[] statements in the exception-throwing `if` branches.