Jpeg quality 95 by default with rendering with PIL

This is just my opinion, but when rendering a plot to JPEG, the default quality should be a bit higher.  Plots are usually (admittedly not always) full of starkly defined edges, that don't look very good once the jpeg format gets finished artifacting around all of them.

While it's true that a user shouldn't write a jpeg of something that doesn't consist of smoothly varying colors, if they do, let's try to make it look as good as is reasonable.

I've attached two images, one with the 75 quality and one with 95.  The 75 quality one was 18K in size, and the 95 quality was 30K in size.

![after](https://f.cloud.github.com/assets/1141744/178579/8affe462-7bbf-11e2-986c-621a7f6cc9a2.jpg)
![out](https://f.cloud.github.com/assets/1141744/178580/8ee6dcca-7bbf-11e2-8229-e33e60035892.jpg)