Quality Option Fix

[pdud]

Great plugin you have here! Thanks!

I noticed the same quality issues that were in #1.

These seem to fix the issue :tada:

---

1. Quality settings were always overwritten with the defaults
   • _.extend expects the defaults passed in as the first argument
   • http://underscorejs.org/#extend
2. node-imagemagick only adds the quality option if the format is 'jpg' or 'jpeg'. Currently sending in '.jpg' or '.jpeg'
   • https://github.com/rsms/node-imagemagick/blob/master/imagemagick.js#L393

[andismith]

Thanks for the pull request, I'll merge it in tonight.

[andismith]

Thank you for writing this fix! It's now on npm as version 0.0.4