Add the tests to the gem as per rubyzip/rubyzip#52.

The tests aren't that big and this will help those with a build-test-install
workflow.
Add the pkg directory to .gitignore.
Merge pull request #163 from hainesr/tests-in-gem

Add the tests to the gem as per rubyzip/rubyzip#52.
treat empty file as non-exists
Revert "Speed up Deflater sysread speed when number_of_bytes is small and @output_buffer is large"

This reverts commit a800987a52d115fd599586f210c99e4740e5253f.
Merge pull request #166 from layerssss/master

treat empty file as non-exists
Version bump
Revert "Return created zip file from Zip::File.open when supplied a block"

This reverts commit e3029d0b100257b530ee9ee62df56361d1e76df7.
Version bump