Update to 0.15
- New upstream release 0.15
- Updated the tooling for generating Makefile.PL
- Removed Tie::StdHash from prereqs, which is not require()able as a module
on its own, despite being indexed (GH #3)
- Fixed the addition in release 0.14 of Hash::Util::FieldHash as a
prerequisite (which is not available prior to perl 5.010) for pure-perl
installations (CPAN RT#104435)