New icons for Push/Pull/Bash

I've replaced the labels of the buttons <kbd>Push</kbd> <kbd>Pull</kbd> and <kbd>Bash</kbd> buttons.

In this way the space used by them is decreased and it's even nicer.  
To help people understand what each button does I've added tooltips for:

<kbd>Init</kbd>: Initialize repository
<kbd>![download-alt2c](https://f.cloud.github.com/assets/5382443/2159871/87d594ea-94ae-11e3-9016-0cb6c3b33f5b.png)</kbd>: Git Pull
<kbd>![upload-alt2c](https://f.cloud.github.com/assets/5382443/2159872/8f9e419a-94ae-11e3-9a1f-f965e7ec047f.png)</kbd>: Git Push
<kbd>![terminal2c](https://f.cloud.github.com/assets/5382443/2159873/959c776a-94ae-11e3-882e-8c76c5eb3f81.png)</kbd>: Open Bash console

This is how it looks:
![image](https://f.cloud.github.com/assets/5382443/2159886/29df1b80-94af-11e3-84df-b0c812396fda.png)


I've just a problem with GitHub because I've accidentally submitted again the fix of the Bug icon (Yes I'd like to understand how this stuff works :cry: )