tests added and generation method changed

Hi,

in combination with more recent versions of App::FatPacker, your plugin does not work as intended. Reason js that @INC seems to get handled differently. Only by adding 'lib' into PERL5LIB search path allows to successfully run this plugin. Also the handling for shebang lines was broken due to adding the original-file content after all the fatpacked stuff. By adding the script name to the final fatpack command line, the shebang is handled automatically and is right.

I also added some author-tests allowing to verify that generation works, the generated script has a shebang as its first line and generates the expected output when run.

Hope yo can use this patch.

Best,
Wolfgang