fixing gallery lightbox infobutton style

before
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![image](https://cloud.githubusercontent.com/assets/960919/4302928/c1e4f788-3e5f-11e4-8c67-19a9b975d0e2.png)
after
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![image](https://cloud.githubusercontent.com/assets/960919/4302924/ac91f48a-3e5f-11e4-8358-2445f0381d21.png)