Pod corrections + 2 more test files for more explicit direct sub tests

[ThornyS]

Hi Ron,
I've recently signed up to help contribute to CPAN via the PRC i.e. 'P'ull 'R'equest 'C'hallenge.
I was assigned the GraphViz2 distribution (well, after the first one scaring the bejeezers out of me 'Math::Prime::Util' I asked for a re-assignment) and directed to some helpful ideas on how to make a useful pull request.

I've done the following to generate this current pull request

1. find all .pl and .pm files and run podchecker against them. e.g.
   cd /path/to/GraphViz2
find ./ -name "*.p[lm]" -exec podchecker {} \;
   I found 2 errors, a typo and a head hierarchy clash.
2. This one I am more dubious about as I'm not massively familiar with Devel::Cover in fact this was my first outing with this package. So I ran the following below and looked at the generated ./cover_db/coverage.html e.g.
   cd /path/to/GraphViz2
cover -test
   I'm in doubt as to whether GraphViz2 requires direct sub checking as the scripts/ tests usable examples rather than single function calls. However I've created 2 more specific test files that do just this, so the final coverage.html shows a much greater percentage covering of subs. NB without fully understanding what the tests are doing I've added minimal arguments to these subs so the sub called executes without error. The new test files are below and will run with make test or cover -test
t/test_new.t
t/test_more_methods.t

Please let me know what you think

[ronsavage]

V 2.47 is now on CPAN. See the Changes file for some of the details.