fix overriding fonts

Hello,

I think there is an issue when using the `devicons` class in an element also containing text. If for example i have the following:
```
<a href="http://git-scm.com" class="devicons devicons-git">Git rocks</a>
```
the "Git rocks" text `font-family` will be `devicons` which would reset any custom font inserted.

The solution would be adding the `font-family` to the `:before` pseudo-element. 

I know it's a long shot but what do you think? It gets easily hacked by adding my fix in a custom style though