Make active tab more emphasised, other css changes for tabs

![jabbr-header-styles](https://f.cloud.github.com/assets/1271535/832299/bd9e04f2-f244-11e2-9487-0ed1d45f288e.png)
![jabbr-header-dropdown-styles](https://f.cloud.github.com/assets/1271535/832300/c06f073a-f244-11e2-9919-af81852f81ac.png)