Fix 1px white space in paginator on Chrome OS X


![before](https://cloud.githubusercontent.com/assets/3607926/3943953/14f2ff8a-25db-11e4-9af9-136f4782fc87.png)
The original styles of `#page-nav a, span` will cause 1px hover mismatch in Chrome of OS X, this could be fixed by adding unified line-height and height specification.
![after](https://cloud.githubusercontent.com/assets/3607926/3943958/536be6be-25db-11e4-8c65-3692374c7eb7.png)