Optimizing Post Voting Plugin (png, gif)

Hi,

I performed a test on Zoompf and here are some results about Post Voting Plugin.

Could you please optimize those png ?

Unoptimized Image (PNG) :
- High impact
- Easy to solve

Issue Summary :
This PNG image is needlessly large. This is due to extra data inside the PNG file such as comments or unused palette entries as well as the use of an inefficient DEFLATE compressor. This image can optimized using free tools that would reduce the size of the file without changing or reducing the image quality. These image optimizations are especially important as other optimizations, such as HTTP compression, cannot be applied to images. Optimizing this PNG image will improve server performance while decreasing bandwidth consumption and page load times.

/wp-content/plugins/wpmu-dev-post-votes/img/plusminus/down.png 144 94 34.722%
/wp-content/plugins/wpmu-dev-post-votes/img/qa/down_disabled.png 307 215 29.967%
/wp-content/plugins/wpmu-dev-post-votes/img/qa/down.png 743 500 32.705%
/wp-content/plugins/wpmu-dev-post-votes/img/down_disabled.png 604 495 18.046%
/wp-content/plugins/wpmu-dev-post-votes/img/arrows/down.png 232 177 23.707%
/wp-content/plugins/wpmu-dev-post-votes/img/whitearrow/down.png 419 356 15.036%
/wp-content/plugins/wpmu-dev-post-votes/img/plusminus/down_disabled.png 147 96 34.694%
/wp-content/plugins/wpmu-dev-post-votes/img/whitearrow/down_disabled.png 466 382 18.026%
/wp-content/plugins/wpmu-dev-post-votes/img/arrows/down_disabled.png 270 193 28.519%
/wp-content/plugins/wpmu-dev-post-votes/img/arrows/up.png 237 184 22.363%
/wp-content/plugins/wpmu-dev-post-votes/img/plusminus/up.png 154 107 30.519%
/wp-content/plugins/wpmu-dev-post-votes/img/qa/up.png 733 491 33.015%
/wp-content/plugins/wpmu-dev-post-votes/img/whitearrow/up.png 393 347 11.705%
/wp-content/plugins/wpmu-dev-post-votes/img/up_disabled.png 576 495 14.063%
/wp-content/plugins/wpmu-dev-post-votes/img/up.png 590 508 13.898%
/wp-content/plugins/wpmu-dev-post-votes/img/qa/up_disabled.png 292 210 28.082%
/wp-content/plugins/wpmu-dev-post-votes/img/arrows/up_disabled.png 264 193 26.894%
/wp-content/plugins/wpmu-dev-post-votes/img/plusminus/up_disabled.png 181 110 39.227%
/wp-content/plugins/wpmu-dev-post-votes/img/whitearrow/up_disabled.png 443 386 12.867%
/wp-content/plugins/wpmu-dev-post-votes/img/down.png 633 521 17.694%

And a gif :
/wp-content/plugins/wpmu-dev-post-votes/img/loading.gif 2,530 2,244 11.304%

Best Regards,
Laurent