Log Message:
Update to 2.0.6

Upstream changes:
2.0.6 Tue Oct 22 16:17:06 UTC 2013
        [ENHANCEMENTS]
        - MARC::Field->as_string() now accepts an optional second
          parameter to specify the delimiter to use between
          subfields. (Tomas Cohen Arazi)
        - MARC::Field->delete_subfield() can now accept a regexp
          to specify the subfields to remove.  For example, to
          remove all numeric subfields, one can say:

          $field->delete_subfield(code => qr/\d/);

          (Jason Stephenson)
        [FIXES]
        - the warnings pragma is now used throughout MARC::Record
        - $field->as_string('0') now returns the contents of
          subfield $0 rather than the contents of all of the
          subfields in the field.
        - RT#88421: add newline after printing warnings
          (Jason Stephenson)
        - RT#85804: fix spelling glitch (Gregor Herrmann)

2.0.5 Mon Feb 11 20:39:10 PST 2013
        - fix use of qw(...) in test case so that module passes
          tests with Perl 5.17.x.

2.0.4 Sat Feb  9 19:01:47 PST 2013
        [ENHANCEMENTS]
        - add MARC::Field->set_indicator($indpos, $indval), a mutator
          for indicators
        - add MARC::Field->set_tag to allow tags to be renamed
          (Robin Sheat)
        - delete_subfield(), if given a single subfield label as its
          argument, will delete all instances of the specified
          subfield, increasing its DWIM factor
        - improved POD for MARC::Field->delete_subfield()
        [FIXES]
        - RT#70346: delete_subfield() no longer clears entire field if
          arguments are badly formatted
        - croak if invalid arguments are passed to delete_subfield()
        - fix error in tutorial (thanks to Tom Burton-West for the
          catch)
        - RT#76990: emit leader of correct length even if record longer
          than 99,999 octets (Julian Maurice)
        - RT#67094: croak with correct error if attempting to create
          MARC::Field sans subfields
        - corrected POD for indicator() method
        - move tag validity check to new class method,
          is_valid_tag($tagno)
        - move indicator validity check to new class method,
          is_valid_indicator($indval)
        - have MARC::Record pass perlcritic --gentle (mostly)
        - remove function prototypes
          (see http://www.perlmonks.org/?node_id=861966)