Merge pull request #8 from chipdude/master

cosmetic: remove inconsistent tabs
Require Perl 5.006 to get pack 'q' for quads.  Thirteen years is long enough.
Fix signedness of integer packing and unpacking (signed were treated as unsigned).
Introduce Net::AMQP::Value::* classes to control packing of table values, with
  all the convenience overloads necessary to make them harmless outside tables.
Support packing and unpacking of full range of signed and unsigned integer values,
  though broker differences may make their use problematic.
In tables, pack and unpack values from the "boolean" module as AMQP booleans.
In tables, pack and unpack undef as AMQP "void".
Packaging the previous change.
doc updates