Fixed sort block returning undef bug.

When I fixed the unequal number of digits bug in lookup_by_versionstring(), I
completely changed the algorithm. This algorthm assumed that perl was okay with
sort blocks returning undef, my Perl setup tested fine, but according to CPAN
Testers the warning was expaned in a later version of Perl, and the warning is
even a fatal error on some Perl setups the CPAN Testers tested fetchware on.

So, this patches fixes that by discarding any files from @versionstrings that
have an empty versionstring, so sort no longer sees any undefs to warn or die
over.
Added additional tests for lookup_by_versionstring().

They test for unequal number of version numbers:
6.3.9
6.3
6
5.3.9
5.3
5.0
Added SKIP block to skip new's tests if there is no terminal according to -t.

This fixes some CPAN Testers FAILs due to STDIN not being a proper terminal,
which borks all of the Term::ReadLine->new('fetchware test') calls.
Fixed POD typo regarding verify_method.
Fixed weird t/bin-fetchware-upgrade.t CPAN Testers bug with verify_method.

Added verify_method 'md5'; to make_test_dist()'s Fetchwarefile template only use
md5 for verification instead of trying gpg, then sha1, andthen finally trying
md5, which is what will actually work. I know it will work, so I should say so.
v1.007

    - Fixed a bunch of CPAN Testers FAILs. Including:
        - Weird t/bin-fetchware-upgrade.t test-dist fail bug.
        - Added SKIP block unless -t to t/bin-fetchware-new.t testing.
        - Fixed sort block returning undef bug, and added extra tests too.