Add ROS name validation function and tests.
Merge pull request #8 from hersh/pub-callbacks

Added connect and disconnect callbacks, message-events, GetNumPublishers()
Add namespace testing functions
Add name canonicalization function.
Fix name validation of single character special names.
Apply go fmt.
Add argument processing function and test.
Added support for talking to c++ ros nodes.
C++ ROS nodes seem to use a slightly different xmlrpc encoding.  This should
enable both python and C++ nodes to talk to rosgo nodes.