add the ability to set upload/download rate-limits (in kB/sec.) on shared torrents
add javadoc documentation for upload/download rate-limit functionality
reduce rate limit code duplication by refactoring code present in both InboundThread and OutboundThread to a common ExchangeThread superclass.
add example of upload/download rate limiting to the client usage sample.
add comments documenting the drawbacks/potential improvements for the download/upload rate limiting algorithm
minor formatting/style modifications based on feedback from pull request #49