fixes for the build process

See #8
If I've removed MANIFEST I've got a error like:
$ rm MANIFEST && perl Makefile.PL && make dist
Writing Makefile for g-cpan
Writing MYMETA.yml and MYMETA.json
rm -rf g-cpan-0.16.5
/usr/bin/perl5.18.2 "-MExtUtils::Manifest=manicopy,maniread" \
	-e "manicopy(maniread(),'g-cpan-0.16.5', 'best');"
Problem opening MANIFEST: No such file or directory at /usr/lib64/perl5/5.18.2/ExtUtils/Manifest.pm line 347.