Exclude quickdraw tests from releases

[djfpaagman]

I was checking the structure of the gemspec, and noticed that it does not have the quickdraw test files in the regex for files that are excluded.

I did some additional digging and it seems like we could also ignore these:

• fixtures/
• config/
• bench.rb

Let me know what you think, happy to add a commit to add those.

[joeldrapper]

Thank you!