:xs_core_only works, test could use work
cleaned up tests, separated logic a bit more to enable testing
s/caller/module/
tidied
docs
parse using version.pm
added dep on version.pm
Clean up use of perl version numbers

Removes use of version.pm.  Uses numeric form of Perl's version.
Adds correct Module::CoreList dependency for is_core().
modernize meta files
Make test_module_in_core private
tidy code
added .travis.yml
Implement :xs_core_or_dual

This option allows core modules or upgraded dual-life modules.

The code paths have been streamlined.
Drop support for Perl < 5.006 and refactor monkey-patches
.mailmap