Refactored error handling via introduction of Kafka::Exceptions module

- Use of Try::Tiny for proper preservation of $@.
- Removed RaiseError, last_error and last_errorcode methods.
- Error handling is done using the module Exception::Class.
- Updated documentation.
- Added Kafka::Connection->cluster_errors method.
- Improved tests and Kafka::Cluster for support of Perl 5.10 and 32-bit systems.
Change-Id: I77690cf56d784afd49aabb1878f6a5e4fec59d23
small fix in docs

Change-Id: If59c94798fb41ba7a17705957605dc1a72b45194