Fixed all non-passing tests in call_spec.

The only non-passing tests remaining (though there are admittedly a lot, I think they're all related) are in wrapper_spec.rb.
Partially fixes Issue #36 

The tests I fixed were failing because they relied on the exported files from pdftk being exactly identical to a file contained within the gem. This can't ever be guaranteed to be platform/version-independant since even an inconsistency in the order in which the PDFs array of properties enumerates itself (which could be caused by something as simple as a compiler optimization) would cause the test to fail. I parsed the data in these failing tests with a regex and converted them to a hash before comparing and the tests then matched.

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Also, @tcocca, I am interested in working more on this project and fixing it up to get it live on RubyGems. I think I can figure out the other testing bugs. I only had a few hours to play with it right now and got pretty far so I thought I'd make this pull request.

Is there any way I could contact you so we can chat briefly at some point if you'd be interested?