BBC: Use image sizes closer to the display sizes, make signal high

This makes the detailed episode image bigger and the tiled episode smaller, and gives the spice a high signal because the triggers are very specific.
Old sizes
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Desktop view
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![Desktop view](https://cloud.githubusercontent.com/assets/2399307/2877818/9d594fde-d453-11e3-974a-f3be83e71454.png)
Mobile view
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Wouldn't load...
Updated sizes
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Desktop view
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![Desktop view](https://cloud.githubusercontent.com/assets/2399307/2877749/989b6da2-d452-11e3-96a2-24413d0606f4.png)
Mobile view
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![Mobile view](https://cloud.githubusercontent.com/assets/2399307/2877766/d0ba4988-d452-11e3-9496-8e3121ce6a05.png)