Adding the ability to hide the share button

I've added a customization flag for disabling the share button (asked by my client).

| Before | After |
| ------------- | ------------- |
| ![saeros_pull_before](https://cloud.githubusercontent.com/assets/562587/2798544/a49091c8-cc50-11e3-9b47-4dfc9721eb24.png)  | ![saeros_pull_after](https://cloud.githubusercontent.com/assets/562587/2798543/a473a158-cc50-11e3-95a5-43906790ddee.png)  |