Changes for version 1.21
- Improve make_position() to support HMS UTC timestamp. make_position() now returns the packet type character so that it can signal the presence of a timestamp.
- Improve make_position() to support comment string, !DAO! extension, altitude encoding. Fix rounding errors in lat/lon/speed. Support generating packets with no speed or course. Take optional parameters in a hash parameter. Implement unit tests for make_position().
- Set up Travis for automatic unit test runs.
- Additional character escaping in regular expressions to deal with deprecated functionality in Perl 5.22.