LPS-39273 Primary buttons in Site Memberships don't look like primary

![site_memberships_-_liferay](https://f.cloud.github.com/assets/203395/1008287/fd5aaee4-0b1f-11e3-932d-c42f2912d0cd.png)

![site_memberships_-_liferay 2](https://f.cloud.github.com/assets/203395/1008288/ff7330a2-0b1f-11e3-8860-6420e2f273d7.png)